Chemistry

All matter consists extremely small indivisible particles called atom. Atoms of elements are identical in all aspects. Atoms of different elements are quite different. Atoms can neither be created nor be destroyed. Atoms of one element can't transferred to atoms of another element. Atoms always combine in whole number ratio to form compound atom (molecule). The relative number and types of atoms present in a molecule of a compound is always same.

Depending on the types of atoms present in a molecule of a substance, molecules are classified as Homoatomic molecule and Heteroatomic molecule. Homoatomic Molecule: This type of molecule contains only one type of atom. Eg. H2, O2, P4 etc. Depending on the number of atoms present in a molecule, homoatomic molecules are further classified as monoatomic, diatomic, Polyatomic (Triatomic, Tetraatomic and so on). Eg. Monoatomic He, Zn etc. Diatomic O2, Cl2, N2 etc. Triatomic O3 Tetraatomic P4 Octaatomic S8 Heteroatomic Molecule: This type of  molecule contains different types of atoms molecules of compounds are heteroatomic molecules ex:- CO2,PH3 (Phosphine Gas),CO3…

Atom: An atom is the smallest particle of an element which can take part in chemical reaction. Atom consists sub-atomic particles like electron, proton, neutron etc. Molecule: Molecule is the smallest particles of substance and has free existance eg. H2, N2,CO2, NH3 etc.