What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
The two properties of carbon which lead to the huge number of carbon compounds are:
Catenation: Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. These compounds may have long chains of carbon, branched chains of carbon, or even carbon atoms arranged in rings. Carbon atoms may be linked by single, double, or triple bonds. The carbon-carbon bond is very strong and stable, which allows a large number of compounds with many carbon atoms linked to each other.
Tetravalency: Since carbon has a valency of four, it is capable of bonding with four other atoms of carbon or atoms of some other element. Compounds of carbon are formed with oxygen, hydrogen, nitrogen, sulphur, chlorine and many other elements, giving rise to compounds with specific properties.
Explanation
The textbook clearly states these two factors in section 4.2. Catenation (from Latin 'catena' meaning chain) is carbon's unique ability to bond with itself, forming chains, branches, and rings. Tetravalency refers to carbon's valency of four, allowing it to form four covalent bonds with other elements. Together, these properties enable carbon to form millions of compounds, outnumbering all other elements combined.