Question

Why is the chemistry so rich?

Answer 1

Why? Because carbon can `"catenate..."`

Explanation:

And what does `"catenate"` mean in this context? It means carbon can form `C-C` chains.......

And thus for the alkanes, we start with `CH_4`, `"methane".` And we can make a carbon-carbon bond and form `"ethane"` `H_3C-CH_3`...and we can KEEP doing this....`"propane, butane, pentane, etc."` all the way up to impossibly long alkanes....

And thus the alkanes form a so-called homologous series whose general formula we can specify as `C_nH_(2n+2)`...and such alkanes have reasonably similar chemistry. Stick a functional group in there, i.e. `OH` to give alcohols, or `X` to give alkyl halides, you generate other families of organic compounds.