GCSE Chemistry · Chemistry
Chemical bonding: a clear study guide
Bonding questions become easier when you connect the particles and forces in a structure to the properties you observe. Name the particles first, then explain the attraction and movement.
Ionic bonding
Ionic bonding forms when electrons transfer from one atom to another, creating positive and negative ions. The ions are held in a giant lattice by strong electrostatic attractions between opposite charges.
Ionic compounds have high melting points because many strong attractions must be overcome. They conduct electricity when molten or dissolved because the ions can move, but not when solid because the ions are fixed in place.
- Metals usually form positive ions by losing electrons.
- Non-metals usually form negative ions by gaining electrons.
- The formula must balance the total positive and negative charge.
Covalent and metallic structures
Covalent bonding is the sharing of pairs of electrons between non-metal atoms. Simple molecules have strong bonds within each molecule but weaker intermolecular forces between molecules; giant covalent structures have bonds throughout a large lattice.
Metallic bonding consists of positive metal ions surrounded by delocalised electrons. The mobile electrons explain why metals conduct electricity, while layers of ions can slide so metals are malleable.
Link structure to properties
A strong answer names the structure, identifies the force or particle that matters and then links it to the property. Avoid saying that a substance is strong or conductive without explaining what moves or what must be overcome.
Quick check
Why can molten ionic compounds conduct electricity?
Answer: Their ions are free to move and carry charge.
What particles move through a metal to carry current?
Answer: Delocalised electrons.
Common questions
Why do simple covalent molecules often have low melting points?
The covalent bonds inside each molecule are strong, but the forces between molecules are relatively weak and require less energy to overcome.
Why does graphite conduct electricity?
Each carbon atom has one delocalised electron that can move through the layers and carry charge.