Atom The smallest particle of an element which does not exists in free state but take part in chemical reaction.
Type of atom
i) Electropositive atom
ii) Electronegative atom
The atom of metal are called electropositive atom. They have tendency to lose electron in order to get stable configuration.
The atom of non-metal are called electronegative atom. They have tendency to to gain electron in order to get stable configuration.
The atoms which have tendency to lose as well as to gain electron is called as metalloid. For example Se, Ge, etc
Molecule The smallest particles of compound which exists free state a posses the characteristics of element or compound.
Types of Molecule
i) Monoatomic He, Ne
ii) Diatomic Hydrogen, Nitrogen
iii) Triatomic Carbondioxide
Discovery of atom In 1808 John Dalton put forwarded his theory, it is as following
1) Matter is composed of extremly tiny particles is called as atom.
2) Atoms of same element or compound are identical.
3) Atoms of different element or compound are different in all aspects.
4) Atoms can not destroyed, created and transformed from one elements to another elements.
5) Atoms combine together in simple whole number ratio to give compound.
6) The relative number & kinds of atom are constant in a given compound.
Molecular formula It is the symbolic representation that shows actual number of atoms of different kinds present in one molecule of that substance.
Qualitative Significance of molecular formula
1) Name of that compound
2) Atoms of different elements combined to form that molecule
1) Number of atoms of different elements in one molecule of that substance
2) Relative weights
3) One molecule of that substance
4) One molecular weight of that substance
5) One gram molecular weight or more precisely one mole of that compound
6) Structural formula represents actual arrangement of atom involved
Valency Valency of an element is the number of hydrogen atom or twice the number of oxygen atom with which one atom of the element combine.
Modern concept of valency It is defined as the number of electrons gain, lost or shared
Wednesday, December 15, 2010
9:48 PM surendra