Six Elements, and One of Them Has Four Hands

Almost everything you are made of comes down to six elements: carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur — CHNOPS. One of them does something the others cannot. Carbon has four valence electrons, so it makes four stable covalent bonds, and four is the number that buys chains, branches and rings. Everything after this topic is that skeleton with small clusters of atoms hung off it — and those clusters, not the skeleton, are what decide how a molecule behaves.

AP BIOLOGY · 8 STEPS · 6 QUICK CHECKS · CHNOPS ≈ 97% BY MASS · CARBON = 4 BONDS · ORGANIC = CARBON-BASED · v1