Ionic, Covalent, Dative and Metallic Bonding

Ionic bonding is electrostatic attraction between oppositely charged ions in a giant lattice; smaller, more highly charged ions attract more strongly. Metallic bonding is attraction between cations and delocalised electrons. A covalent bond is a shared pair attracted to both nuclei; in a dative (coordinate) bond both electrons come from one atom ( $\mathrm{NH_4^+}$ , $\mathrm{Al_2Cl_6}$ ). Head-on orbital overlap gives a σ bond; sideways p-orbital overlap gives a π bond. Period 3 atoms can expand the octet ( $\mathrm{PCl_5}$ , $\mathrm{SF_6}$ ).

Cambridge 9701 Paper 1Cambridge 9701 Paper 2Edexcel YCH11 WCH11AQA 7405 Paper 1≈ 45 minRevision 1 · updated 2026-10-30

Section 1 of 14

Learning objectives

Describe ionic, metallic, covalent and dative bonding.
Explain σ and π bonds and hybridisation.
Relate bond strength and length.
Explain physical properties from structure and bonding.

Pause and think

Why does magnesium oxide melt at 2852 °C but sodium chloride at only 801 °C?

Section 2 of 14

Core idea

Start hereFour ways to hold atoms together

Diamond, salt, copper and ammonium chloride are held together in completely different ways. The type of bond decides whether a substance melts, conducts or dissolves.

The big idea

Ionic: electrostatic attraction between ions. Metallic: cations and delocalised electrons. Covalent: shared pairs, including dative bonds. Orbital overlap gives σ and π bonds.

1. σ and π bonds

Orbital overlap

Drawing diagram…

Head-on vs sideways.

Worked exampleBonds in a molecule

Count σ and π bonds in propenenitrile, $\mathrm{CH_2{=}CH{-}C{\equiv}N}$ .

Goal: Totals.
Strategy: Each bond has 1 σ; extra bonds are π.

$\text{C–H}: 3\sigma$
Three H atoms.
$\text{C=C}: 1\sigma+1\pi;\ \text{C–C}: 1\sigma$
Double and single.
$\text{C}\equiv\text{N}: 1\sigma+2\pi$
Triple bond.

Answer6 σ and 3 π.

✓ Checkσ bonds:

3+1+1+1=6

✓.

Key takeawayDative bonds Shown by an arrow from donor to acceptor. Once formed, a dative bond is identical to other covalent bonds.

Pause and think

Why is silicon dioxide a solid but carbon dioxide a gas?

Summary

Ionic, metallic, covalent, dative.
σ + π.
Structure explains properties.

Dative bond: Covalent bond where both electrons come from one atom.
Sigma bond: Bond formed by head-on orbital overlap.
Pi bond: Bond formed by sideways overlap of p orbitals.

HistoryLinus Pauling. Linus Pauling introduced hybridisation and electronegativity in the 1930s; his book The Nature of the Chemical Bond won him the 1954 Nobel Prize.

Fun factAluminium chloride's double life. Aluminium chloride vapour is made of Al₂Cl₆ dimers held together by dative bonds, but at higher temperatures it splits into AlCl₃ molecules.

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