Organic chemistry is the study of carbon compounds, which form a vast array of molecules due to carbon's unique properties. Carbon atoms have an exceptional ability to bond with each other to form long straight chains, branched chains, or rings, a property called catenation. Carbon also readily forms stable covalent bonds with other elements like hydrogen, oxygen, nitrogen, and halogens. Additionally, carbon can form single, double, or triple covalent bonds. The different ways these atoms can be arranged within a molecule, such as in butane and 2-methyl propane, further contribute to the immense variety of organic compounds. That's 2 down. 3 left today — send the next one.