Carbon and how to draw it

Carbon makes four bonds and bonds strongly to itself, so it can build chains, branches and rings of any length. That's why there are millions of organic compounds and only a few thousand of everything else put together.

A molecular formula only counts atoms: C₄H₁₀. A structural formula draws every atom and bond. A condensed formula writes each carbon with its hydrogens in a line: CH₃CH₂CH₂CH₃ is butane. Different molecules can share a molecular formula, so chemists draw structures.

The skeletal (line) formula is the shorthand everyone uses. Each line is a bond, each corner and each line end is a carbon, and hydrogens on carbon aren't drawn: you fill in enough to give each carbon four bonds. Other atoms (O, N, Cl) and the hydrogens on them are written in. A zigzag of three lines is four carbons, butane.

The shape follows the bonds. A carbon with four single bonds points them to the corners of a tetrahedron, about 109.5° apart, so chains are really zigzags. A carbon with a double bond is flat, about 120°; one with a triple bond is straight, 180°.

Six carbons in a ring with alternating double bonds make benzene, C₆H₆, drawn as a hexagon with a circle or three double bonds inside. Its electrons are shared around the whole ring, which makes it unusually stable. Rings like it are called aromatic.