Language of Chemistry

The universe is composed of matter and energy. Matter and energy are inter-convertible to each other. The branch of modern science which deals with the study of composition, transformation and property of matters is known as Chemistry. Chemistry can be classified as:

a.      Physical Chemistry

b.      Iorganic Chemistry and

c.       Organic Chemistry

Element:

An element is defined as pure substance which can neither be decomposed into nor built from simpler substance by any kind of physical or chemical methods. Eg: Hydrogen, Oxygen, Carbon, Sodium etc. The concept of element was first introduced by Robert Boyle.

Atom:

The smallest particle of an element which can take part in chemical change is called an atom. It may or may not be capable of independent existence.

Compound:

A Compound is a substance produced by union of two or more elements in a definite proportion. t can be decomposed into two or more simple substance. Eg:

Water- H2O

Glucose- C6H12O6

Ammonia- NH3 etc.

Molecule:

A molecule is defined as the smallest unit (particle) of any kind of substance, elements or compounds which can exist independently and can possess all properties of substance. Eg: H2, O2, O3, P4, S8, H2O etc.

Homonuclear Molecule: Molecule formed by the combination of similar kinds of atoms are called homonuclear molecule. Eg: O2, O3, P4, S8 etc.

Heteronuclear molecule: Molecule formed by the combination of different kinds of atoms of different elements are called heteronuclear molecule. Eg: CH4, PCl5, H2O etc.

Symbol: Symbol is defined as the abbreviation or shorthand sign for the full name of an element. One or more letter(s) is used to write the symbol of an element.

Eg: Hydrogen        H                                                                                                                                      

      Oxygen            O

      Magnesium     Mg

      Uranium           U

      Vanadium        V

      Antimony         Sb

      Gold                  Au

      Curium             Cm

      Nobelium         No

      Americium       Am

      Plutonium         Pu

Valency:

Valency of an element is the combining capacity of the element which is measured in terms of hydrogen atoms or its equivalent which combine with one atom of that elements. Examples:

Elements       Valency

H                       1

O                      2

N                      3

Al                     3

Ca                    2

Na                    1

Certain elements can have more than one valency that is they exhibit variable valency. Eg:

Fe-  2 and 3

Cu- 1 and 2

Sn- 2 and 4 etc.

The compound in which the metal has lower valency is called an “ ous “ compound while the compound in which the metal has higher valency is called “ ic “ compound.

Eg: Fe= 2 valency FeCl2, Ferrous chloride

      Fe= 3 valency FeCl3, Ferric chloride

Radical:

A radical may be defined as an atom or group of atoms having positive or negative charge and behaves as a single unit in chemical change.  

Some Common Radicals

Monovalent Radicals

1.  Ammonium       NH4

2.  Hydroxide         OH

3.  Cyanide              CN

4.  Nitrite                NO2

5.  Chlorate            ClO3

6.  Amide               NH2 etc.

Divalent Radicals:

1. Carbonate        CO3

2. Oxalate              C2O4

3. Sulphite              SO3

4. Zincate               ZnO2

5. Stannite             SnO2

6. Stannate          SnO3 etc

Trivalent Radicals:

1. Aluminate         AlO3

2. Arsenite            AsO3

3. Arsenate           AsO4

4. Ferricyanide     Fe(CN)6 etc.

Dalton’s Atomic Theory: (John Dalton, In 1808)

Postulate:

1.      All matter consists of extremely small individual particles called atoms.

2.      Atoms of same elements are all alike.

3.      Atoms of different elements are entirely different and have different properties.

4.      Atoms can neither be created nor be destroyed, it can only be transformed to one form to another.

5.      Atoms combines together in simple whole number ratio to give compounds.

6.      The relative number and kinds of atoms are constant in a given compound.

Stoichometry:

Stoichometry is the branch of chemistry which deals with the weight relationship in chemical reaction and weight relationship that prevails in a chemical compound.

Law of Chemical Combination:

1.      Law of conservation of mass

2.      Law of definite proportion

3.      Law of multiple proportions

4.      Law of reciprocal or equivalent proportions

5.      Law of gaseous volume