Question

What is the reason of formation of millions of organic compound

Answer 1

The reason lies within the uniqueness of carbon's structure and bonding capabilities. Carbon has four valence electrons and therefore makes four separate covalent bonds in compounds.

Answer 2

Organic compounds mean - “Carbon based.” Carbon is unique in the periodic table (silicon is a close 2nd), in that it has 4 valence electrons. That means each individual carbon atom can bind to 4 other atoms of almost any variety, and each of those 4 can bind to 4 others, etc., etc., This leads to organic compounds having incredible variety and complexity - short chains, long chains, ring structures, branched structures, on and on. The capacity for variability is almost infinite.