Chemistry · Bonding, Structure and Properties of Matter
Covalent Bonding
Spec 5.2.1.4📙 Higher
Interactive · share a pair step by step
Theory · read, then commit
Covalent bonding happens between non-metal atoms. Instead of transferring electrons, they share pairs of electrons — and each shared pair is one covalent bond.
Checkpoint · quick check
Describe what is meant by a covalent bond.
1️⃣Single bond — 1 shared pair
H₂ shares one pair. So do H₂O (O–H), NH₃ (N–H) and CH₄ (C–H).
2️⃣Double bond — 2 shared pairs
O₂ shares two pairs. CO₂ has two C=O double bonds.
3️⃣Triple bond — 3 shared pairs
N₂ shares three pairs — which makes it very stable.
Checkpoint · quick check
State the number of single covalent bonds present in a water molecule, H₂O.
⚠️ Common Mistake
Students often say that covalent bonds must be weak because substances like water have low boiling points. The covalent bonds themselves are actually very strong. The low melting and boiling points come from the weak intermolecular forces BETWEEN whole molecules — when the substance melts, those weak forces are overcome, not the strong covalent bonds inside each molecule.
Retrieval · Match the Molecule to its Bonding
⭐ Higher Tier Only
Draw dot-and-cross diagrams for: H₂, Cl₂, HCl, O₂ (double bond), N₂ (triple bond), CH₄, H₂O, NH₃, CO₂. Show lone pairs on relevant atoms. Understand bond polarity in terms of electronegativity differences. The shared electrons are attracted to both nuclei — electrostatic attraction is the covalent bond.
Test yourself · 10 questions, exam order
⭐Examiner Tip
Never call covalent bonds weak. To explain a low boiling point, the marks are for the weak intermolecular forces between molecules being overcome — the covalent bonds inside each molecule are strong and stay intact.
0 of 10 answered
Warm-up · 2 questions
Carbon (Group 4) bonds with hydrogen to form methane, CH₄. Determine how many covalent bonds a carbon atom forms.
Explain why oxygen exists as O₂ molecules rather than as single O atoms.
Exam standard · 4 questions
Explain why a chlorine molecule (Cl₂) contains a single covalent bond.
Explain, in terms of electrons, why a nitrogen molecule (N₂) contains a triple bond.
A dot-and-cross diagram of carbon dioxide shows O=C=O. Explain how this arrangement gives every atom a full outer shell.
Explain why simple molecular substances have low melting and boiling points, despite containing strong covalent bonds.
Stretch · 4 questions
Compare a single, a double and a triple covalent bond in terms of the number of shared electrons.
Ammonia is NH₃. Deduce the number of covalent bonds nitrogen forms, and explain why.
Explain why the boiling points of the halogens increase from fluorine to iodine, even though each molecule contains a single covalent bond.
A dot-and-cross diagram shows only the outer-shell electrons. Explain one limitation of using it to represent a molecule such as methane.
Key note · cover it, say it, check it
Revision card · 7 stepsCovalent Bonding
01Covalent bonding: non-metals share electron pairs.
02Each shared pair = one covalent bond.
03Both atoms achieve full outer shells.
04Single bond: 1 shared pair.
05Double bond: 2 shared pairs.
06Covalent bonds within molecules are STRONG.
07Intermolecular forces between molecules are WEAK → low melting points.
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