Double and triple bonds

Carbon can use two or three hands on the same partner. Here is what that looks like.

Two atoms can share two pairs of electrons. That is a double bond, drawn as two lines. They can even share three pairs: a triple bond, drawn as three lines.

Carbon still has 4 lines in total. In ethene, C₂H₄, the double bond uses 2 of each carbon's 4 lines, so each carbon has room for only 2 hydrogen atoms. In ethyne, C₂H₂, the triple bond uses 3, which leaves room for just 1.

Double bonds can join carbon to other atoms too. In carbon dioxide, CO₂, the carbon shares two pairs with each oxygen atom: two double bonds, so carbon still has 4 lines. You will meet the C=O double bond again in a later lesson.

Ethane, ethene and ethyne sound alike because chemists build names from parts. You will learn how the names work a little later.