Single, Double, and Triple Bonds:
• Each atom contributes ONE electron
• Represented as a single line: H-H, H-Cl, C-H
• Examples: H₂, HCl, CH₄, H₂O
• The most common type of covalent bond
• Each atom contributes TWO electrons
• Represented as a double line: O=O, C=O
• Examples: O₂, CO₂
• Stronger and shorter than single bonds
• Each atom contributes THREE electrons
• Represented as a triple line: N≡N
• Example: N₂ (nitrogen gas)
• Very strong — this is why nitrogen is so unreactive!
Common Molecules You Must Know:
• Each H has 1 electron, needs 2 for full shell
• Share 1 electron each → 1 shared pair
• Single bond: H-H
• Both now "have" 2 electrons (like helium)
• O has 6 outer electrons, needs 8
• Each H has 1 electron, needs 2
• O shares 2 electrons (one with each H)
• Each H shares 1 electron with O
• O gets 8, each H gets 2 — everyone's happy!
• Formula shows 2 H atoms bonded to 1 O
• Each O has 6 outer electrons, needs 8
• Each O needs to gain 2 more electrons
• Solution: share 2 pairs of electrons (double bond)
• O=O (double bond)
• Both O atoms now "have" 8 electrons
• Each N has 5 outer electrons, needs 8
• Each N needs 3 more electrons
• Solution: share 3 pairs of electrons (triple bond)
• N≡N (triple bond)
• This is why nitrogen gas is so stable and unreactive!
• C has 4 outer electrons, needs 8
• Each H has 1 electron, needs 2
• C forms 4 single bonds with 4 H atoms
• C gets 8, each H gets 2
• Tetrahedral shape (3D pyramid)
Counting Tip: An atom needs to make enough bonds to complete its outer shell. H needs 1 bond (to get 2 electrons), O needs 2 bonds (to get 8), N needs 3 bonds (to get 8), C needs 4 bonds (to get 8).
This deep dive covers Understanding Different Types of Covalent Bonds within Covalent Bonding for GCSE Chemistry. Revise Covalent Bonding in Bonding & Structure for GCSE Chemistry with 25 exam-style questions and 21 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 3 of 13 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Covalent Bonding
Which of the following best describes a covalent bond?
Explain the difference between a bonding pair and a lone pair of electrons in a covalent molecule.