Click any atom or bond in this page — anywhere — and it will tell you exactly what it is, why it bonds that way, and how you could build it yourself. Start with the ethane molecule on the right.
☝ click an atom or a bond to beginCarbon has 4 electrons to share, and it's always looking to complete a set of 8 (the octet rule). It does this by sharing electron pairs with neighboring atoms — each shared pair is one bond. Sharing one pair makes a single bond, sharing two pairs makes a double bond, and sharing three makes a triple bond. Click each pair below to see how the carbon–carbon bond changes shape, angle, and reactivity as it goes from single to triple.
A plain carbon chain (drawn here as R) is fairly unreactive. Everything interesting in organic chemistry happens when you replace a hydrogen with a functional group — a small cluster of atoms bonded on with its own new bond. That new bond is what gives the molecule a new personality: a new smell, a new reaction, a new name. Click any atom or bond in the icons below.
Any carbon chain long enough can bend around and bond to its own tail — the last carbon forms a new C–C bond with the first one, closing a ring. Cyclohexane below is just hexane bent into a loop. Benzene looks similar, but its electrons don't stay put — they spread evenly around the whole ring, which is what makes it aromatic. Click the bonds and the dashed circle to see the difference.
Once you can build a molecule, naming it is just describing what you built, piece by piece. Click a piece of the name below — or the matching part of the structure — to see what it's telling you.