Glossary

Acidity

The acidity of a base is defined as the number of ionizable hydroxyl groups in its molecule.

Anode

It is an electrode through which electrons enter the external circuit.

Alpha Rays

There are positively charged particles emitted from a radioactive substance. They carry two positive charges and are called helium nuclie.

Analytical Chemistry

It is the branch of chemistry which discusses the analytical methods forgetting information about chemical compounds and chemical processes.

Atomic Number

Number of positively charged particles (protons) present in the nucleus of an atom.

Atomic Size

Average distance between the nucleus of an atom and its outermost electronic shell. Its units are nm or pm.

Arrehenius Acid

It is a chemical compound which gives proton (H+) in water.

Arrehenius Base

It is a chemical compound which gives hydroxide ion (OH-) in water.

Atomic Spectrum

Spectrum of radiations emitted by the excited atoms when they come to the normal state.

Acidic Salts

An acidic salt is obtained when hydrogen atoms present in an acid, are partially replaced by metallic atoms.

Alchemist

A scientist trying to convert cheaper metals into precious metals is called Alchemist and this branch of chemistry is called Alchemy.

Atomic Mass

The mass of an element relative to the unit mass, which is 1/12th o the mass of C-12.

Ampere

The amount of electric current which liberate one electrochemical equivalent of a substance per second during electrolysis of that substance is called ampere.

Biochemistry

It is the study of chemical compounds present in living things.

Balancing of Chemical Equations

Equating the atoms of reactants with those of products.

Beta Rays

These are electrons emitted from a radioactive substance.

Brownian Movement

The free movement of the molecules of gases and liquids is called Brownian movement.

Bronsted Acid

A compound which can donate proton.

Bronsted Base

A compound which can accept proton.

Basicity

The basicity of an acid is defined as the number, of ionizable hydrogen atoms present in its molecule.

Basic Salts

A basic salt is obtained when the hydroxyl groups present in a base are partially replaced by some other groups.

Boiling Point

A temperature at which a liquid changes into gaseous state.

Chemistry

The branch of science, which deals with the composition of matter changes in matter and the laws or principles which govern these changes.

Chemical Equation

The representation of a chemical change in terms of symbols and formulas.

Covalent Solid

A solid in which there exist a covalent bond between atoms.

Covalent Bond

It is the force of attraction that arises between two atoms due to mutual sharing of an electron pair.

Co-Ordinate Covalent Bond

When the shared pair of electrons is provided by one of the bonded atoms, a coordinate covalent bond is formed.

Cohesive Forces

The forces of attraction present between the particles of solid, liquid and a gas.

Cathode Rays

Rays emitted from cathode in the discharge tube.

Colloidal Solution

A solution in which solute particles are bigger than those present in a true solution and which cannot be filtered.

Conductor

A substance which allows electric current to pass through it.

Cathode

It is an electrode through which electrons leave the external circuit.

Concentration of a Solution

The amount of a solute which has been dissolved in a particular amount of a solvent.

Concentrated Solution

A solution, which contains an excess amount of a solute as compared to that of a solvent.

Cell

The vessel containing reacting substances in which transfer of electrons takes place is called cell.

Coulomb

It is unit of electric current. When one ampere electric current is passed for one second the quantity of electric current is one coulomb.

Discharge Tube

A glass tube containing a gas at a very low pressure and provided with electrodes to study the passage of electricity through the gas.

Dipole-Dipole Forces

The forces of attraction which originate due to the difference in electro negativities of the bonded atoms in polar molecules.

Diffusion

The movement of molecules from a higher concentration to a Lowr concentration is called Diffusion.

Dilute Solution

A solution, which contains a small amount of a solute as compared to that of a solvent.

Double Salts

When two typical salts are crystallized together a double salt is formed. The physical properties of the crystals of double salt are different from those of the component salts.

Doberiner’s Law of Triads

Dobereiner arranged similar elements in sets of three, called Triads. Atomic mass of the middle atom of a triad was equal to the average of the atomic masses of first and third members.

Degree of Ionization

It is the extent to which an electrolyte ionizes in water.

Experiment

An experiment is an activity performed under suitable conditions with specially designed instruments to get the required information.

Empirical Formula

The formula of a compound which shows the minimum ratio present between the atoms.

Electron Affinity

The amount of energy given out when an electron is absorbed in the outermost electronic shell of all isolated gaseous atom. Its units are KJ/mol.

Electro-Negativity

It is the power of an atom to attract the shared pair of electrons.

Evaporation

The continuous escape of the molecules of a liquid from its surface.

Elastic Collision

When gas molecule collides with each other their total energy does not decrease or increase. This type of collision is called an elastic collision.

Electrolytic-Cell

In a non-spontaneous oxidation-reduction reaction takes place with the help of electrical energy.

Electro-Chemistry

It is that branch of chemistry in which chemical energy is converted into electrical energy or electrical energy is converted into chemical energy.

Electrolytes

When electricity is passed through an ionic compound which is either in the fused state or in the form of aqueous solution, it is decomposed into its constituents. The ionic compound is called an electrolyte.

Electrolysis

The passage of electricity through an electrolyte is called electrolysis.

Electrochemical Series

A list of ions in which they are arranged in the order of their ability to get discharged.

Electroplating

The process of depositing a metal on another metal with the help of electricity.

Exothermic Reaction

Those chemical reactions during which heat is evolved.

Endothermic Reactions

Those chemical reactions in which heat energy is absorbed.

Enthalpy of Reaction

Heat of reaction which takes place at constant pressure.

Formula Mass

Formula mass is the mass of compound relative to the unit mass which is 1/12th of the mass of C-12.

Farad

It is the unit of charge 1 farad = 96500 coulomb.

Fusion

When a solid change into liquid this phenomena is called Fusion.

Heat of Neutralization

The heat given out during a neutralization reaction is called heat of neutralization.

Heat of Reaction

Heat evolved or absorbed during a chemical reaction which takes place at pressure.

Hypothesis

In the light of experiments, the scientists try to explain observations and facts. This tentative explanation is called hypothesis. It is quite possible that after sometime, on the basis of new experiments this hypothesis may be rejected.

Hydrogen Bonding

When a hydrogen atom is attached to any one of fluorine, oxygen and nitrogen atoms, there appears strong dipole forces which are called hydrogen bonding.

Hydrated Ions

Ions of a solute surrounded by water molecules are called hydrated ions.

Ionization

An electrolyte splits up into charged particles upon heating or in its aqueous solution. This process is called Ionization.

Ionic Theory

A theory which explains the process of electrolysis.

Intermolecular Forces

The forces of attraction present between the molecules of a compound.

Ionization Energy

The minimum amount of energy required to remove an electron from the outermost electronic shell of an isolated gaseous atom. Its unit is KJ/mol.

Ionic Bond

A bond formed due to the electrostatic force of attraction between oppositely charged ions.

Ionic Solid

A solid which is made up of ions of opposite charges.

Isotope

Atoms of an element having the same atomic number but different mass number.

Inorganic Chemistry

The study of all elements and their compounds except carbon is called inorganic chemistry.

Industrial Chemistry

The application of chemical knowledge in technology and industry and the preparation of industrial products are called industrial chemistry.

Inference

To deduce results after coordinating the observed facts with integrated scientific knowledge is called inference.

Kinetic Theory

The theory which explains the composition and properties of all the three states of matter.

Lewis Acid

A substance which can accept an electron pair.

Law

A theory when repeatedly gives the same results after experimentation and offers correct explanation of scientific facts it then becomes a law or principle.

Law of Conservation of Mass

Total mass of reactants is equal to that of products during a chemical reaction.

Law of Definite

A compound always contains elements combined together in a fixed ratio by mass.

Law Multiple Proportions

When two elements combine together to give more then one compounds, the different masses of an element, which combine with the fixed mass of the other element, have a simple ratio between them.

Law of Reciprocal Proportions

When two or more elements A and B combine separately with the fixed mass of the third element E the ratio in which they do so may be the same or some simple multiple of the ratio in which these two elements (A and B) combine with each other.

Molar Solution

A solution in which one mole of a solute has been dissolved in one dm3 of solution. It is represented as M.

Metallic Bond

When positively charged metal ions are held together by freely moving electrons, the bond formed is called a metallic bond.

Molecular Solid

A solid which has Vander Waal’s forces present between its molecules.

Melting Point

A temperature at which a solid changes into a liquid.

Mass Number

The total number of protons and neutrons present in the nucleus of an atom.

Mendeleyv’s Periodic Law

Properties of elements are a periodic function of their atomic masses.

Modern Periodic Law

Properties of elements are a periodic function of their atomic numbers.

Molecular Mass

Molecular mass is the mass of an element or a compound relative to the unit mass, which is 1/12th of the mass of C-12.

Molar Mass

The mass of an element or a compound which contains Avogadro’s number particles.

Molecular Formula

The formula of an element or a compound which tells the actual number of atoms present in the molecule of that element or a compound.

Neutralization

Acids and bases react together to form salts and water and in this way they neutralize the properties of each other. This reaction is called Neutralization reaction.

Normal Salts

Salts, which neither have replaceable hydrogen atoms nor hydroxyl groups.

Non-Conductor

A substance through which electric current cannot pass.

Neutron

It is the smallest neutral particle present in the nucleus of atoms. Its mass is slightly more than that of a proton.

Nucleus

Central part of an atom where most of its mass is concentrated. Its size is very small as compared to the size of the atom.

Newland’s Law of Octaves

If elements are arranged in the increasing order of their atomic masses every 8th element repeats the properties of the 1st element.

Oxidation

A chemical reaction in which oxygen is added or hydrogen is removed or electrons are lost.

Octet Rule

When an atom has eight electrons in its outer most shell, its is said to be stable and does not combine with other atom to reduce its energy. This is called octet rule.

Organic Chemistry

The branch of chemistry in which we study the compounds of carbon.

Observation

The process of observing natural phenomena with the help of five senses and the scientific equipment.

Orbits

The circular path of an electron around the nucleus.

pH Scale

The negative log of hydrogen ion (H+) concentration present in a solution is called pH. This scale measures the concentration of hydrogen ions present in a solution.

Percentage by Mass

Volume of a solute present in 100cm3 of a solution.

Percentage by Volume

Volume of a solute present in 100 cm3 of a solution.

Physical Chemistry

The branch of chemistry, which deals with the physical properties and physical behaviour of material things.

Prediction

The inference based on observed facts.

Proton

It is the smallest positively charged particle present in all kind of atoms. The mass of this particle is equal to the mass of the hydrogen nucleus (H+).

Positive Rays

Rays produced in the discharge tube, which are traveling in a direction opoposite to the cathode rays.

Reversible Reaction

Chemical reaction, which takes place both directions, forward as well as backward.

Reduction

A chemical reaction in which hydrogen is added or oxygen is removal or electrons are absorbed.

Radioactive Rays

Rays emitted from radioactive element or their compounds, which can cause fogging of the photographic plate.

Strong Acid

An acid which ionizes completely in water.

Strong Base

A base which can ionize completely in water giving excess of hydroxide ions.

Sublimation

Some solids, upon heating, change directly into vapors instead of changing into liquid.

Scientific Method

The method which helps to collect facts on the basis of observations and experiments. Theories and laws are then formulated to explain these facts.

Solute

The substance present in relatively lesser amount in a solution.

Solvent

The substance present in excessive amount in a solution.

Solvated Ions

Ions of a solute surrounded by solvent molecules in a solution are called solvated ion.

Saturated Solution

A solution, which contains the maximum amount of a solute at a particular temperature and which is unable to dissolve further amount of solute in it.

Supersaturated Solution

A solution which contains an amount of solute more than that required for the preparation of a saturated solution at a particular temperature.

Standard Solution

A solution whose concentration is known.

Solubility

The amount o solute in grams which can dissolve in 100 gm of solvent at a particular temperature to give a saturated solution.

Suspension

A mixture in which solute particles do not dissolve in solvent.

Strong Electrolytes

An electrolyte which completely ionize in water.

Transition Elements

Elements having incomplete penultimate (next inner to the outermost) electronic shell.

Theory

If a hypothesis is accepted (after discussion and experimentation) it is called a theory.

Thermo Chemistry

It is the branch of chemistry in which we study the heat changes during a chemical reaction.

Unsaturated Solution

A solution, which can dissolve further amount of a solute at a particular temperature, is called unsaturated solution.

Unified Atomic Mass Unit

Unit of a new scale, which is equal to 1/12th of the mass of C-12.

Voltaic Cell

In a cell a spontaneous oxidation-reduction reaction is used to produce electric current.

Weak Electrolyte

An electrolyte which undergoes partial ionization in water.

Weak Base

A base which ionizes partially in water.

Weak Acid

An acid which ionizes partially in water.

Water of Crystallization

The number of water molecules present in the crystals of a solid

Differences

Metals and Non Metals

Metals

1. Metals have luster shine surface.
2. Metals reflect heat and light.
3. Metals conduct heat and electricity
4. Metals are ductile and can be drawn into wire.

Non-Metals

1. Non-Metals have no luster.
2. Non-Metals usually don’t reflect heat and light.
3. Non-Metals do not conduct heat and electricity.
4. Non-Metals are non ductile and cannot be drawn into wire.
5. Non-Metals are non-malleable and can not form sheets.

Homogeneous and Heterogeneous Mixture

Homogeneous Mixture

1. Those mixtures, which have uniform composition throughout their mass are called homogeneous mixtures.
2. Homogeneous mixture has only one phase through out its mass.
3. Homogeneous mixture are also known as solution.
4. Examples: Salt and water, Sugar and water.

Heterogeneous Mixture

1. Those mixtures, which do not have uniform composition through their mass are called Heterogeneous Mixture.
2. Heterogeneous Mixture has more than one phase through out its mass.
3. Heterogeneous Mixture are not solutions.
4. Examples: Rocks, Soil, Food products.

Molecular and Empirical Formula

Molecular Formula

1. Formula which shows the actual number of atoms of each element present in a molecule is called Molecular Formula.
2. Molecular Formula shows the structure of compound.
3. Two or more compounds cannot have same Molecular Formula.
4. Molecular Formula = n x Empirical Formula.
5. It represents covalent compounds only.

Empirical Formula

1. formula, which shows the relative ratio of atoms of each element present in a molecule, is called Empirical Formula.
2. Empirical Formula can not show the structure of compound.
3. Two or more compounds can have same Empirical Formula.
4. Empirical Formula = Molecular Formula / n
5. It represent an ionic compound as well as a covalent compound.

Symbol and Formula

Symbol

1. A symbol is an abbreviation for the chemical name of an element and represents only one atom of the element.
2. It represents one atom of an element.
3. Symbol is written for elements.
4. Examples: Na, Br, Cl, F etc.

Formula

1. Representation of compound in terms of symbols is called formula. It represents one atom of an element.
2. It represents atoms of same or different elements present in one molecule.
3. It represents an ionic compounds as well as a covalent compound.
4. Examples: H2O, NH3 etc.

Gram and Gram Molecule

Gram

The atomic mass of an element expressed in grams is called gram atomic mass.
2. It is associated with element only.
3. It is the mass of one atomic mole.
4. One gram atom of any substance contains 6.02 x 10(23) atoms. (23 is the power of 10).

Gram Molecule

1. Molecular mass of any element or compound expressed in grams is called gram molecule.
2. It is associated with element and compound.
3. It is the mass of one molecular mole.
4. One gram molecule of any substance contains 6.02 x 10(23) atoms. (23 is the power of 10).

Atom and Molecule

Atom

1. It is the smallest particle of an element which can enter into a chemical reaction.
2. It is represented by a symbol of the element.
3. It shows the properties of the element.
4. It retains its identity in a chemical reaction.

Molecule

1. It is the smallest particle of a substance which can exist and show all the properties of the substance.
2. It is represented by a molecular formula of the substance.
3. It shows the properties of the substance.
4. It does not retain its identity in a chemical reaction.

Exothermic and Endothermic Reactions

Exothermic Reaction

1. Those chemical reactions in which heat energy is evolved are called exothermic reactions.
2. In exothermic reactions the enthalpy of products is lower than the reactants. H is therefore negative for an exothermic reaction.
3. During endothermic reaction, the system becomes colder and net potential energy of substance increases.
4. The energy is absorbed during these reactions.
5. The temperature of reaction therefore decreases.

Endothermic Reactions

1. Those chemical reactions in which heat energy is absorbed are called endothermic reactions.
2. In endothermic reactions the enthalpy of reactants is lower than the products. H is therefore positive in endothermic reaction.
3. During endothermic reaction, the system becomes colder and net potential energy of substance increases.
4. The energy is absorbed during these reactions.
5. The temperature of reaction therefore decreases.

Physical and Chemical Properties

Physical Properties

1. The physical properties of a substance are those characteristics which serve to distinguish it from other substance but do not deal with its ability to undergo chemical changes.
2. These are related to the physical state of matter.
3. Examples: Formation of ice from water, formation of a magnet from ice etc.

Chemical Properties

1. The chemical properties of a substance indicate the ability of a substance to undergo chemical changes.
2. They are related to the chemical change of a substance.
3. Examples: burning of paper, rusting of iron.

Electrolyte and Non-Electrolyte

Electrolytes

1. Electrolytes conduct electricity in molten or in solution form.
2. These form positive and negative ions when dissolved in water e.g. NaCl form Na+ and Cl- ions when dissolved in water.
3. Chemical changes occur when electric current is passed through the electrolyte.
4. Generally these are ionic or polar covalent compounds.

Non-Electrolytes

1. Non-electrolytes do not conduct electric current in molten or in solution form.
2. These do not form positive and negative ions when dissolved in water e.g. Urea, sugar, glucose etc.
2. No chemical change occurs in them on passing current.
3. Generally these are non polar covalent compounds.
4. Generally these are non polar covalent compounds.

Acid and Base

Acid

1. Those compounds which provide hydrogen ion (H+) in aqueous solutions are called Acids.
2. An acid is a substance which produces H+ ions in aqueous solution.
3. Acid is a species (a compound or ion) which donates or tends to donate a proton (H+).
4. An acid is a species (molecule or ion) which can accept a pair of electron. An acid is also called an electrophile (electron loving).
5. They have sour taste.
6. Acid turn blue litmus red methyl orange red.

Base

1. Those compounds, which provides hydroxyl (OH-) ion in aqueous solution, are called bases.
2. A base is a substance, which gives (OH-) in aqueous solution.
3. A base is a species, which accepts or tends to accept a proton.
4. A base is a species (molecule or ion) which can donate a pair of electrons. A base is also called a nucleophile (Nucleus loving).
5. Bases have bitter taste.
6. Bases turn red litmus to blue, colorless phenolphthalein to pink and methyl orange to yellow.

Ionic and Covalent Bond

Ionic Bond

1. Ionic bond is formed by complete transfer of electrons from one atom to another atom.
2. Ionic bond is always formed between different atoms. E.g. NaCl, CaCl2.
3. In ionic bond atoms have very large electro-negativity and ionization energy difference.
4. This bond is usually formed between metals and non-metals.
5. This bond is very strong.
6. As a result of this bond ionic compounds are formed.
7. It is always formed between two different atoms.
8. It is formed when difference of electro-negativity of combining atoms is 1.7 or more.

Covalent Bond

1. Covalent bond is formed by the mutual sharing of electrons between two atoms.
2. Covalent bond may be formed between similar or dissimilar atoms e.g. H2, O2, HCl etc.
3. In covalent bond atoms have very small electro-negativity or ionization energy difference.
4. This bond is usually formed between non-metals only.
5. This bond is comparatively less strong.
6. As a result of this bond covalent compounds are formed.
7. It is formed between similar and different types of atoms.
8. It is formed when difference of electro-negativity of combining atoms is less than 1.7.

Ionic and Covalent Compounds

Ionic Compounds

1. The ionic compounds are usually solid, hard and brittle.
2. The ionic compounds are good conductors of electricity either in fused state or in the form of aqueous solution.
3. Ionic Compounds have high melting points and boiling points.
4. Ionic compounds have high melting points and boiling points.
5. Covalent compounds are mostly volatile.

Covalent Compounds

1. Covalent compounds exist in all the three states i.e. gas, liquid and solid.
2. A pure covalent compound does not conduct electricity.
3. These have usually low melting and boiling points.
4. These are soluble in water.
5. These are insoluble in water but soluble in organic solvents.

Co-Ordinate Covalent and Covalent Bond

Co-Ordinate Covalent Bond

1. It is a bond in which the shared electron pair is denoted by one atom only.
2. One atom donates electrons but other has no contribution.
3. Lewis acids and bases always from this bond.
4. It is represented by ->.
5. It is formed by the donation of an electron apir by one of the two bonded atoms.
6. It is formed by the completely filled atomic orbital.

Covalent Bond

1. It is a bond formed by the mutual sharing of electrons.
2. In the shared electron pair both atoms have equal contribution.
3. Lewis acids and bases do not form this bond.
4. It is represented by _.
5. It is formed by the mutual sharing of electrons between atoms.
6. It is formed by the overlap of partially filled atomic orbital.

Polar and Non-Polar Covalent Bond

Polar Covalent Bond

1. The covalent bond between two atoms having different electro-negativity is called a polar covalent bond.
2. In a polar bond, the shared electron pair is not equally attracted by the bonded atoms.
3. Bonded atoms become slightly charged and acquire partial =ve and -ve charges.
4. It has an ionic character.
5. The bond energy is greater.

Non-Polar Covalent Bond

1. The covalent bond between two atoms having same electro-negativity is called a non-polar covalent bond.
2. In a non polar bond, the shared electron pair is equally attracted by the bonded atoms.
3. Bonded atoms remain electrically neutral and do not acquire partial charges.
4. It has no ionic character.
5. The bond energy is lesser.

Electrolytic and Galvanic or Voltaic Cell

Electrolytic Cell

1. It is a device for converting electrical energy into chemical energy. It means by passing current through an electrolyte, chemical reaction takes place.
2. It consists of a vessel containing an electrodes and a source of direct current (battery).
3. Example: Electrolysis of aqueous solution of NaCl.

Galvanic or Voltaic Cell

1. It is a device for converting chemical energy into electrical energy. It means spontaneous redox reaction is used for the production of electric current. This cell was prepared by L.Galvani and A.Volts, hence named as Galvanic or Voltaic Cell.
2. It consists of two half-cells. Each half cell consists of an electrodes and the solution with which it is in contact.
3. Example: Daniel Cell-Zn/ZnSO4 and Cu/CuSO4 cell.

Solution and Suspension

Solution

The size of particles is between 0.1 to 1nm.
2. Particles cannot be seen with low power microscope.
3. It is homogeneous.
4. Particles do not settle down.
5. It is transparent.
6. Components cannot be separated by filtration.

Suspension

1. The size of particles is larger than 1000nm.
2. Particles can be seen by low power microscope.
3. It is heterogeneous.
4. Particles settle down.
5. It is not transparent.
6. Components can be separated by filtration.

Electro-Chemistry

Electro-Chemistry

The branch of chemistry which deals with the study of chemical energy to electrical energy or electrical energy to chemical energy is called electro-chemistry.

Conductors

Those substances through which electric current can pass are called conductors. For example all metals are conductors.

Non-Conductors

Those substances through which electric current cannot pass are called non-conductors. For example plastic, wood are non-conductors.

Electrolysis

The process in which electricity passes through the aqueous or infused state of some substance. The substances itself decompose into its component. This process is called electrolysis.

Electrolyte

The compound in molten state or in aqueous solution through which electricity can pass are called electrolyte.

Non-Electrolyte

Those compounds through which electricity cannot pass are called non-electrolyte.

Strong Electrolyte

The substances which are highly soluble and completely ionized are called strong electrolyte. For example acids, bases and salts are strong electrolytes.

Weak Electrolyte

The substances which are not highly soluble and remain in un-ionized form are called weak electrolyte.

Electroplating

A process in which metal is deposited on the surface of another metal by electrolysis is called electroplating.

Objectives of Electroplating

Decoration

It is done for decoration. Noble and precious metals like gold or silver are deposited on the inferior metals to enhance their beauty and look beautiful.

Protection

Electroplating is done to protect the metals from rusting as well as from attack of other substance like organic acids and acidic gases.

Repair

It can be used to repair the broken machinery by electroplating with other metals. Usually the metals like copper, silver, chromium, nickel and gold are used for electroplating.

Procedure of Electroplating

The metal which is to be electroplated is first cleaned with sand and then washed with caustic soda solution and finally with a lot of water.
This metal is made cathode and the metal which is going to be deposited is made anode. The electrolyte is a salt of metal being deposited and electroplating is carried out in a tank made of cement, glass or wood. It is called an electrolytic tank.
The electrolyte should have following properties:
1. It must be very soluble in water.
2. It must be good conductor.
3. Cheap
4. May not easily oxidized or reduced or hydrolyzed.
(Diagram)

Solution and Suspension

Solution

A homogeneous mixture of different chemical substances which has uniform chemical composition through out and shows uniform physical properties is called solution. For example dissolve a small amount of copper sulphate in water the water will become blue. If this blue liquid is filtered, it will pass through the filter paper without leaving any solid. The mixture thus prepared is called a solution.

Binary Solution

A solution which is formed by mixing two substances is called binary solution. For example solution of glucose and water.

Solute

The component of a binary solution which is in lesser amount is called solute. For example in copper sulphate solution, copper sulphate is solute.

Solvent

The component of a binary solution which is in greater amount is called solvent. For example in copper sulphate solution, water is solvent.

Saturated solution

A solution in which maximum amount of a solute has been dissolved at a particular temperature and in which the dissolved form of solute is at equilibrium with its undissolved form is called saturated solution.

Unsaturated Solution

Solution which can dissolve further amount of a solute at a [particular temperature is called an unsaturated solution.

Supersaturated Solution

The solution which contains even more amount of solute required to prepare saturated solution is called super saturated solution. The hot saturated solution of compound like sodium thiosulphate does not crystallize its solute if cooled slowly without disturbance. Such a solution is called supersaturated solution.

Dilute Solution

A solution which contains small amount of a solute as compared to the solvent is called dilute solution.

Concentrated Solution

A solution which contains excess amount of a solute as compared to that of a solvent is called a concentrated solution.

Concentrated Solution

The amount of solute present in given quantity of solvent is called concentration of solution. The concentration of a solution can be expressed in many ways depending upon the amount o solute and solvent present in it.

Concentration of Solution

The amount of solute present in given quantity of solvent is called concentration of solution. The concentration of a solution can be expressed in many ways depending upon the amount of solute and solvent present in it.

Percentage by Mass

The percentage of solute by mass is the mass of solute present in hundred part of the solution. For example 5% hydrogen peroxide solution by mass means that 5g hydrogen peroxide are dissolved in 95g of water to give 100g of solution.
Percentage of Mass = (Mass of Solute/Mass of Solution) x 100

Percentage by Volume

The concentration unit expresses the volume of solute present in 100cm3 of solution. For example 15% solution of alcohol by volume will mean that 15cm3 alcohols are present in 100cm3 of solution. (Here 3 represents cube)
Percentage by Volume = (Volume of Solute/Volume of Solution) x 100

Molar Solution

The solution that contains one mole of solute in 1dm3 of solution is called a molar solution. The concentration of this solution is expressed as M.

Molarity

Molarity of a solution is the number of moles of solute present in 1dm3 of the solution. It is expressed as M.
M = Number of Moles of Solute/Volume of Solution in dm3
or
M = (Mass of solute/Molecular Mass) x (1/ Volume of Solution in dm3)

Crystallization

The process in which crystal separates from saturated solution on cooling is called crystallization. It is a useful process because it can be used to purify the impure solid compounds. It can also be used to separate a mixture of solids.

Hydration

The ions surrounded by solvent molecules in solution are called solvated ions. If water is a solvent these ions are called hydrated ions.

Suspension

A suspension in such a mixture in which solute particles do not dissolved in solvent and if filtrated its particles do not pass through the pores of filter paper.

Colloidal Solution

In a colloidal solution the solute particles are slightly bigger than those present in a true solution but not big enough to seen with naked eye.

Standard Solution

A solution whose molarity (strength) is known is called Standard Solution.

True Solution

A True Solution is such a mixture in which solute particles are completely homogenized in the solvent for example solution of sodium chloride or copper sulphate in water.

Solubility

Solubility o a solute in a particular solvent is defined as the amount of solute in grams, which can dissolve in 100g of the solvent at a particular temperature to give a saturated solution.
or
The amount of a solute in gram moles, which can dissolve in one kilogram of the solvent at a particular temperature, to give a saturated solution.

Factors Affecting the Solubility

Effect of Solvent

Similar solvents dissolve similar solutes, i.e. if the chemical structure and the electrical properties such as dipole moment of solute and solvent are similar, the solubility will increase. If there is dissimilarity in properties, then either the solute will not dissolve or there will be very little solubility.

Effect of Solute

Different solutes have different solubility’s in a particular solvent e.g. if the saturated solutions of table sugar and sodium chloride are prepared, it is found that the concentration of sodium chloride solution is 5.3 molar while that of sugar solution is 3.8 molar. In other words, the solubility of sodium chloride in water is far greater than that of sugar. This is due to the fact that the attraction of sodium (Na+ and chloride (Cl-) ions with water is greater than that of sugar molecules with water.

Effect of Temperature

Change in temperature has different effects on the solubility of different compounds. Usually the solubility increase with the increase in temperature but it cannot be taken as a general rule. The solubility of compounds like lithium carbonate, calcium chromate decreases with the increase in temperature. The solubility of gases in water also decreases with the increase in temperature. On the other hand, there are a large number of compounds whose solubility in water increase with the increase in temperature e.g. sodium nitrate, silver nitrate, Potassium chloride etc. the solubility of sodium chloride in water does not increase appreciably with the increase in temperature.

States of Matter

States of Matter

Matter has three states:
1. Gas
2. Liquid
3. solid
These are physical states of matter. The three states of one matter may have different physical properties while their chemical properties are same. Water exists in three physical states solid (ice), liquid and gas(steam) has same chemical properties.

Kinetic Theory of Matter

The Kinetic theory was presented to explain the properties of gases and is called kinetic theory of gases. But this theory was also able to explain the composition of liquid and solid state of matter. So its is called Kinetic Theory of Matter.
According to Kinetic Theory of matter:
1. All matter is composed of atoms, molecules or ions.
2. These particles have kinetic energy due to which they are in the state of motion.
3. In gaseous state, these particles move in a straight line. They collide with one another and with the walls of container. In liquids the rate of their movement is very small but in solids, there is to and fro motion only.
4. Generally material particles can have three types of movements, i.e. translational, rotational and vibrational.

Solids

The state of matter which has definite shape and volume is called solid.

Properties of Solids

1. Definite Volume and Shape

The cohesive forces in solid substances are so strong that they keep their particles arranged in fixed positions. So due to restrict movements of particles, the solids have definite volume and shape.

2.Motion of Particles

The solid particles have vibrational motion only because these particles are held in fixed position by strong cohesive forces.

3. Effect of Heat

The physical state of solid substance can be changed by heating. On heating solid is converted to liquid and gaseous state. Heat increases the kinetic energy of the particles and they start vibrating at higher frequency. At a particular temperature the vibrational motions become fast that they overcome the cohesive forces and solid melts to liquid.

4. Melting Point

The temperature at which the solid is converted to liquid on heating is called melting point. At melting point, the particles of solid loose their means position and their arrangement. The solid collapses and turns to liquid.

5. Sublimation

The conversion of some solids directly into gaseous state on heating is called sublimation. Iodine, ammonium chloride and naphthalene change directly into vapour state upon heating.

Liquid

The state of matter having definite volume but indefinite shape is called liquid.

Properties of Liquid

1. Volume

Liquids have definite volume. In liquid particles are very close to one another and have cohesive forces among the particles. Due to the presence of cohesive forces, liquids have definite volume and keep their level as well.

2. Shape

Liquids do not have any specific shape. They adopt the shape of the container. The molecules of liquid are able to move. Due to this random motion the molecules of liquid do not have fixed position and as a result, a liquid does not have any specific shape.

3. Evaporation

Conversion of liquid into its vapours at any temperature is called evaporation. The molecules of liquid come to the surface of liquid and escape by overcoming cohesive forces. So liquid is converted to vapours at all temperature.

4. Boiling Point

The temperature of a liquid at which its vapour pressure becomes equal to the atmospheric pressure is called boiling point.

Gas

The state of matter which does not have definite shape and volume is called gaseous state.

Properties of Gaseous State

1. Indefinite Volume and Shape

In gaseous state, the molecules have insignificant cohesive forces among themselves. They move very fast in all possible directions. As a result, a gas neither has fixed shape nor a fixed volume.

2. Kinetic Energy of the Particle of a Gas

Gas particles have very high kinetic energy as compared to liquid and solid state.

3. Pressure

The molecules of a gas are in the state of random motion. The molecules of gas not only collide with one another but also with the walls of the container in which they are enclosed. Due to their collision, the velocity of the molecules changes every moment. The pressure exerted by gas is also due to the collision of its molecules with the walls of the container.

4. Elastic Collision

The collision of gas molecules is elastic in nature which means that the total energy of the colliding molecules remains the same before and after the collision.

5. Kinetic Energy

The kinetic energy of molecules of gas is very high as compared with solid and liquid.

Diffusion

The movement of molecules from a higher concentration to a lower concentration is known as Diffusion.
If the concentration of molecules at a particular place is higher, they start moving towards a place where their concentration is lower. When the concentration of molecules at both the places becomes equal the process of diffusion stops.

Diffusion in Gases

The molecules of one gas can diffuse easily into the molecules of other gas. For example if an open bottle of a perfume is kept in a room, its smell will spread uniformly throughout the room. The liquid perfume present in the bottle volatilized slowly and its vapours diffuse through out the room.

Graham’s Law of Diffusion

Scottish Chemist, Thomas Graham (1833) discovered that lighter gs can diffuse through porous pot faster than the heavier one. This is called Graham’s

Law of Diffusion.

Hydrogen being lighter gas will diffuse faster than oxygen or carbon dioxide.

Diffusion in Liquids

Liquid molecules can also diffuse because they have free movement. Since the molecules of liquid move comparatively slowly than gas molecule, their rate of diffusion are also lesser than gases.

Brownian Movement

Robert Brown (1927) discovered this phenomenon:
The free movement of the molecules of gases and liquid is called Brownian Movement.”

When a pollen grain is put in water. The movement of pollen grain in water is observed by microscope. It is observed that pollen grain is continuously moving in all directions. This free movement of pollen grain was due to the free movement of water molecules. The colliding water molecules will also force pollen grain to move as well. The students can observe Brownian movement with the help of simple experiment.

Experiment

Put a drop of milk on a microscope slide and cover it with cover slip. Put it under microscope and observe it. You will see small particle of fat moving randomly in milk. The movement of fat particles is actually due to the movement of water molecules in milk.

Periodicity of Elements and Periodic Table

Definitions

Periodic Table

A table of elements obtained by arranging them in order of their increasing atomic number in which elements having similar properties are placed in the same group is called Periodic Table.

Group

The vertical column of elements in the periodic table are called Groups.

Period

The horizontal rows of elements in the periodic table are called Periods.

Periodicity

The repetition of physical and chemical properties of elements periodically is called Periodicity of Properties.

Periodic Law

Physical and chemical properties of elements are periodic function of their atomic masses.

Metal

Elements which are good conductors of heat and electricity are malleable and ductile and have a metallic luster are called Metals like Sodium, Potassium, Gold, Copper etc.

Non-Metals

Elements which are non or bad conductor of heat and electricity are neither malleable or ductile and have no metallic luster are called Non-Metals like Carbon, Nitrogen, Chlorine etc.

Metalloids

Metalloids are semi metals have the properties which are intermediate between a metal and non-metal like Boron, Silicon, Germanium, Arsenic, Antimony etc.

Law of Triads

A German Chemist, Dobereiner (1829), arranged chemically similar elements in groups of three on the basis of their atomic masses called Triads and it was found that atomic mass of the middle element was approximately equal to the average of atomic masses of other two elements. This is known as Law of Triads.

Drawback or Defect

As very few elements could be arranged in such groups, this classification did not get wide acceptance.

Law of Octaves

An English Chemist Newland (1864) stated that if the elements were arranged in the ascending order of their atomic masses, every eight element will have similar properties to the first. This is knows as Law of Octaves.

Drawback or Defects

1. Noble gases were not discovered at that time and no place was reserved for the undiscovered noble gases.
2. In the same way no blank spaces for the undiscovered elements were present in his table.

Mendeleyv’s Period Table and Periodic Law

Russian Chemist, Mendeleyv’s (186) who wa working separately from Lother Mayer published a table of elements.
According to Mendeleyv’s when the element were arranged in order of their increasing atomic mases, the elements with similar properties were repeated after regular interval and were placed one above the other.A table obtained in this manner is called Periodic Table. Mendeleyv’s stated this periodicity in the form of Periodic Law.

Important Features of Mendeleyv’s Periodic Table

The important features of Mendeleyv’s Periodic table are:

Periods and Groups

The horizontal rows which run from left to right in Periodic Table are called Periods and they are twelve in number.
The vertical rows which run from top to bottom in periodic table are called groups and they are eight in number.

Vacant Spaces

Mendeleyv’s left many vacant spaces for the still unknown elements. For example, next to Calcium (40) should be Titanium (48) but it resembled silicon (28) instead of Aluminium (27). He left vacant space for element with atomic mass 44.

Discovery of New Element

Mendeleyv’s discovered new elements and also guessed their atomic mass and properties.

Atomic Mass Correction

Mendeleyv’s corrected the atomic masses of certain elements on basis of their properties and provided proper place to them in the periodic table.

Defects in Mendeleyv’s Periodic Table

The Mendeleyv’s Period Table has following defects:

Irregular Position of Some Elements

According to Mendeleyv’s Periodic Law Potassium (39) should be placed before Argon (40) but he placed Argon (40) before Potassium (39) which goes against his law.

Position of Isotopes

Mendeleyv’s periodic table gives no indication about the position of isotopes.

Structure of Atom

Mendeleyv’s Periodic table gives no idea about structure of atoms.

Position of Lanthanides and Actinides

Lanthanides and Actinides have not been given proper place in Periodic Table.

Coinage and Alkali Metals

Alkali metals and coinage metals with different properties are placed in the same group. This defect has been replaced by placing them into two sub groups.

Modern Periodic Law and Modern Periodic Table

Modern Periodic Law

Physical and chemical properties of the elements are periodic function of their atomic number. Mosely (1913) says that atomic mas is not fundamental property. Due to some defects present in Mendeleyv’s periodic law, Mosely introduced the concept of anomic number for the elements.

Example
When isotopes were discovered, it was thought advisable to arrange the elements on basis of their atomic number instead o increasing atomic mases. Isotopes were needed different position in the Mendeleyv’s periodic table. Hence Mendeleyv’s periodic law was modified.

Modern Periodic Table

When Mendeleyv’s periodic law was modified and new elements were discovered. This forcd the scientists to change Mendeleyv’s periodic law.
The electronic configuration of atoms also played an important role in he arrangement of the modern periodic law. This form of periodic table is called “Long form of Periodic Table” because it contains eighteen groups instead of eight but seven periods instead of twelve.

Group I – The Alkali Metals

The elements of group I are called “Alkali Metals”. The word alkali is derived from an Arabic word meaning Ashes.

Elements of Group I

Lithium
Sodium
Potassium
Rubidium
Cesium
Francium

Properties of Group I

1. They are mono atomic.
2. They exist in solid metallic state.
3. Outer most shell of these elements is incomplete having one electron.
4. Elements of this group are highly reactive.
5. Elements of this group have large tendency to form compounds.
6. Elements of this group are strongly electro-positive.

Group II – The Alkaline Earth Metals

The elements of group II are called Alkaline Earth Metals. These elements occur in nature as silicate mineral and their oxides and hydroxides are strongly basic. Therefore these elements are called Alkaline Earth Metals.

Elements of Group II

Beryllium
Magnesium
Calcium
Strontium
Barium
Radium

Properties of Group II

1. They are mono atomic.
2. They exist in solid state.
3. Outer most shell of these elements is incomplete having two electrons.
4. Elements of this group are moderately reactive.
5. Elements of this group have moderate tendency to form compounds.

Group III – The Boron or Aluminium Family

The elements of group III exist in solid state.

Elements of Group III

Boron Metalloid
Aluminium Metal
Gallium Metal
Indium Metal
Thallium Metal

Properties of Group III

1. They are mono atomic.
2. They exist in solid state.
3. Outer most shell of these elements is incomplete having three electrons.
4. Elements of this group are quite reactive.
5. Elements of this group have moderate tendency to form compounds.

Group IV – The Carbon and Silicon Family

Elements of Group IV

Carbon
Silicon
Germanium
Tin
Lead

Properties of Group IV

1. They are mono atomic.
2. They exist in solid state.
3. Outermost shell of these elements is incomplete.
4. Elements of this group are quite reactive.
5. Elements of this group have moderate tendency to form compounds.

Group V – The Nitrogen Family

Elements of Group V

Nitrogen
Phosphorus
Arsenic
Antimony
Bismuth

Properties of Group V

1. Some are mono atomic and some are di-atomic.
2. Some of them exist in gaseous and some are in solid state.
3. Outermost shell of these elements is incomplete having five electrons.
4. elements of this group are quite reactive.
5. Elements of this group have quite tendency to form compound.

Group VI – The Oxygen Family

Elements of Group VI

Oxygen
Sulphur
Selenium
Tellurium
Polonium

Properties of Group VI

1. Some are mono atomic and some are di-atomic.
2. Some of them exist in gaseous and some are in solid state.
3. Elements of this group have quite tendency to form compounds.
4. The tendency of forming covalent bond decreases from oxygen to polonium.
5. There is a gradual decrease in the ionization potential down the group.

Group VII – The Halogen Family

Elements of Group VII

Fluorine Gas
Chlorine Gas
Bromine Liquid
Iodine Solid
Astatine Radioactive

Properties of Group VII

1. They are diatomic except At.
2. Halogens are very active non-metals.
3. Outer most shell of these elements is incomplete having seven electrons.
4. Elements of this group are highly reactive.
5. There is a gradual decrease in the ionization potential down the group.

Transition Elements

Definition

Elements in Group IB, IIB, through VIIB are known as Transition Elements because they show their properties which are transitional between higly reactive and strong electro-positive elements of S-block which form ionic compounds and p-block elements which form largely covalent compounds.

Properties of Transition Elements

1. Transition Elements have incomplete inner electron shells.
2. They show variable valency.
3. They show similar behaviour.
4. They all are metals.
5. They have strong inner atomic bonds.

Group 0, The Noble Gases

The elements of Group VIII A are called “Noble Gases” or “Inert Gases” or “Zero Group Elements”.

Elements of Group 0

Helium
Neon
Argon
Krypton
Xenon
Radon

Properties of Group 0

1. They are mono atomic.
2. They exist in gaseous state.
3. Outer most shell of these elements is either complete or contains eight electrons.
4. These elements are mostly chemically non-reactive.
5. These elements have no tendency to form compounds (only a few of these compounds are known).

Atomic Radius

Definition

One half of the distance between the nucleus of two identical atoms when these are in close contact with each other is called Atomic Radius.

Unit

It is measured in angstrom unit A.

Trend in Period

The atomic radii decreases from left to right within a period in the periodic table. This is because nuclear charge increases with the increase of atomic number. But the number of shells remains same within a period.

Trend in Group

Atomic radius increases from top to bottom in a group. This is because, although nuclear charge increases from top to bottom but at the same time on new shell is also added for each successive element down the group.

Ionization Energy (I.E) or Ionization Potential (I.P)

Definition

The minimum energy needed to remove an electron from an isolated, gaseous atom in its ground state is called Ionization Energy.

Unit

It is expressed in electron volts or kilo-joules permole.

1 ev = 96.49kj

Factors Affecting Ionization Energy

The ionization energy of elements depends upon the following factors:

1. Effect of Nuclear Charge on I.E

The greater the nuclear charge the higher is the ionization energy.

2. Effect of Atomic Size

The larger the size of atom the lower is the ionization energy.

Trend of I.E in Period

Ionization energy increases from left to right in a period due to increase in nuclear change and decrease in atomic size.

Trend of I.E in Group

I.E decreases from top to bottom in a group due to increase in atomic size.

Electronegativity

Definition

The tendency of each atom in a covalent molecule to attract a shared pair of electrons towards itself is known as its electronegativity.

Factors Affecting Electronegativity

Electronegativity depends upon the following factors:

Atomic size

Atomic Number

Electron Affinity

Ionization Energy

Trend or Variation in the Period

Electronegativity increases from left to right within a period due to increase in nuclear charge and decrease in atomic size.

Trend or Variation in the Group

Electronegativity values decreases from top to bottom within a group due to increase in atomic size.

Electron Affinity

Definition

The energy change that occurs when an electron is gained by an atom in the gaseous state is known as Electron Affinity.

Electron Affinity for the addition of first electron is negative i.e. energy is released but for further addition of electrons it is positive because energy has to be added to over come repulsion between negative ion and electron.

Unit

It is measured in KJ/mol or in e.v per atom.

Factors Affecting Electron Affinity

Atomic Size

Nuclear Charge

Trend or Variation of Electron Affinity in Group

Down the group in the periodic table, electron affinity decreases because the addition of a new shell to each atom decreases its force of attraction.

Trend or Variation of Electron Affinity in Period

In a period, the electron affinity increases from left to right because the incoming successive atoms have higher nuclear charge and attract electron more towards itself.