Single bonds and chains

Carbon atoms can share a pair of electrons with each other, not just with hydrogen. One shared pair between two carbon atoms is a single bond.

The smallest example is ethane, C₂H₆. Its two carbon atoms are joined by a single bond, and each carbon shares a pair with three hydrogen atoms too. Count the lines around either carbon: 1 to the other carbon plus 3 to hydrogen makes 4, just as lesson 1 promised.

Because each carbon has hands left over, the chain can keep growing. Add more carbons and you get longer chains, like butane, C₄H₁₀, the fuel inside many lighters.