Chemical bonding is the force of attraction that holds atoms or ions together to form molecules or compounds.
Atoms bond to achieve stability, usually by attaining a full outer electron shell (octet rule).
There are three major types of chemical bonds:
An ionic bond is formed when electrons are transferred from one atom to another.
This usually happens between a metal (which loses electrons) and a non-metal (which gains electrons).
Metal atom → loses electrons → forms positive ion (cation)
Non-metal atom → gains electrons → forms negative ion (anion)
Opposite charges attract → bond is formed.
Sodium (Na) + Chlorine (Cl) → NaCl
Magnesium (Mg) + Oxygen (O) → MgO
Calcium (Ca) + Sulfur (S) → CaS
High melting & boiling points
Soluble in water
Conduct electricity when molten or in solution
Crystalline solids
Strong electrostatic forces
A covalent bond is formed when two non-metal atoms share electrons to complete their outer shells.
1 pair of electrons shared
Example: H₂, Cl₂, H₂O
2 pairs shared
Example: O₂, CO₂
3 pairs shared
Example: N₂
Low melting & boiling points
Usually gases or liquids at room temp
Poor electrical conductors
Insoluble in water (mostly)
Form molecules, not ions
One atom donates both electrons for the bond.
Example: NH₄⁺ in ammonium ion.
Metallic bonding occurs in metals when positive metal ions are surrounded by a “sea of delocalized electrons.”
The delocalized electrons move freely, holding the metal together.
Good conductors of electricity
Good thermal conductors
Malleable (can be hammered)
Ductile (can be drawn into wires)
Shiny/lustrous
High melting points (in most metals)
Sodium
Copper
Iron
Aluminium
| Property | Ionic | Covalent | Metallic |
|---|---|---|---|
| Bond type | Electron transfer | Electron sharing | Sea of electrons |
| Types of elements | Metal + non-metal | Non-metal + non-metal | Metals |
| Conductivity | Only when molten/aqueous | No | Yes (solid/liquid) |
| Melting point | High | Low | High |
| Physical state | Solid | Gas/liquid/soft solid | Solid |
| Attraction | Electrostatic | Shared pair | Electrostatic with electrons |
Define ionic, covalent, and metallic bonds.
State two properties of ionic compounds.
Give examples of molecules with single, double, and triple covalent bonds.
Explain why metals conduct electricity.
Differentiate between ionic and covalent compounds.