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
No comments:
Post a Comment