How do we rationalize the chemistry of carbon?
This question is far too open-ended and should be retired....
Entire text-books, and there are many of these, are devoted to organic chemistry. They contain numerous data and details. The ability of carbon to catenate, i.e. form long chains, and form strong bonds with itself, with nitrogen, with oxygen, and with other heteroatoms, generates an extremely rich chemistry, which is also the chemistry of biology.