Six Elements, and One of Them Has Four Hands

You'll learnwhy carbon's four bonds make it the backbone of every biological molecule.

Almost everything you are made of comes down to six elements — CHNOPS — and one of them does something the others cannot. Carbon has four valence electrons, so it makes four covalent bonds, and four is the number that buys chains, branches and rings. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · CHNOPS ≈ 97% BY MASS · CARBON = 4 BONDS · ORGANIC = CARBON-BASED · v6

six elements · carbon’s four hands · the groups that decide

Before you start

What you're looking at

Six element tiles — carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur (CHNOPS) — laid out as an inventory of what life is built from.

The question

Of these six elements, why is carbon the one that can build chains, branches, and rings?

Step 1 / 12