Carbon and its Compounds
Covalent bonding
Learn how atoms share electrons to form covalent bonds.
Your food, clothes, medicines, books, and your own body are mostly made of carbon compounds. So how does carbon bond?
Carbon has electrons 2, 4. To get a full outer shell, could it lose 4 electrons, or gain 4?
- Lose 4 (C⁴⁺): far too much energy is needed to pull away four electrons.
- Gain 4 (C⁴⁻): six protons would have to hold on to ten electrons. That's like one teacher trying to control a huge class: it can't hold them.
Neither works. So carbon does something else: it shares.
A shared pair of electrons between two atoms is a covalent bond. Each atom counts the shared electrons as its own, so both reach a full shell.
| Shared pairs | Bond | Example |
|---|---|---|
| one | single (–) | H–H, Cl–Cl, the C–H bonds in methane CH₄ |
| two | double (=) | O=O |
| three | triple (≡) | N≡N |
Inside a molecule the bonds are strong, but the pull between molecules is weak. So covalent compounds usually have low melting and boiling points: methane boils at 111 K, far below room temperature. They make no ions, so they don't conduct electricity.
Pure carbon comes in different forms, called allotropes. How do we know they are all carbon? Each one burns to give only carbon dioxide.
| Allotrope | Structure | Property |
|---|---|---|
| Diamond | each carbon joined to four others in a rigid 3-D frame | the hardest natural substance |
| Graphite | flat layers of hexagons that slide over each other | smooth, slippery, conducts electricity |
| Fullerene (C-60) | 60 carbons arranged like a football | a newer form; named after the architect Buckminster Fuller |
Practise this lesson
Questions that get harder as you improve, a Tutor that helps without giving the answer away, and progress you can see. Free for every learner.
No account, no email address. Opens the real product.