What is catenation ? How this property varies down the group ?

Explanation

Catenation is the property of carbon atoms to link with one another through covalent bonds. They form straight chain, branched chain or ring structure. For example,

Variation down the group
As we move down the group, atomic size goes on increasing and electronegativity decreases. Therefore, tendency to show catenation also decreases. The order of catenation is `C gt Si gt G ~~ Sn`. Lead does not show catenation.