The elements in group VIII of the periodic table are called noble gases. This is because these gases are inert in nature so are chemically unreactive. The valence electrons in all these gases (except helium) are 8 in number. This is defined as the octet rule. Any atom in order to be chemically stable needs to have 8 electrons in its outer shell. For all elements other than group VIII this is achieved by sharing, gain or loss of electrons between atoms. This results in formation of a chemical bond.
Types of chemical bonds
Ionic: based on gain or loss of electrons between atoms
Covalent: based on sharing of electrons between atoms where electrons from both atoms participate in bonding
Dative or co-ordinate covalent: based on sharing of electrons between atoms where electrons from only one atom participate in bonding
Metallic: present between atoms of a metal
