The catenation tendency of $$C, Si$$  and $$Ge$$  is in the order $$Ge < Si < C.$$   The bond energies $$\left( {{\text{in}}\,kJ\,mo{l^{ - 1}}} \right)$$   of $$C - C,Si - Si$$    and $$Ge - Ge$$   bonds are respectively

Solution :
The linking of identical atoms with each other to form long chains is called catenation. However, this property decreases from carbon to lead. Decrease of this property is associated with $$M-M$$  bond energy which decreases from carbon to lead.