What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?

The two features of carbon that give rise to a large number of compounds are as follows: 

(i) Catenation: It is the ability to form bonds with other atoms of carbon. 

(ii) Tetravalency: With the valency of four, carbon is capable of bonding with four other atoms.

1. Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called calenation.

2. Since carbon has a valency of four, it is capable of bonding with four other atoms of carbon or atoms of some other mono-valent element.