Edexcel GCSE Chemistry · 1CH0
Specification 1.31 · Paper 1, Paper 2
Revise: Formation of Simple Molecular SubstancesElectrons outside the overlaps belong to just one atom; when two occur together, they form a lone pair.
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GCSE Chemistry · key term
A pair of outer-shell electrons that is not shared in a covalent bond.
Used by Edexcel and OCR
Specification 1.31 · Paper 1, Paper 2
Revise: Formation of Simple Molecular SubstancesElectrons outside the overlaps belong to just one atom; when two occur together, they form a lone pair.
Specification C2.2f · Paper 1 (Foundation), Paper 3 (Higher)
Revise: Dot and Cross DiagramsNitrogen's two remaining electrons form one lone pair.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Revise: Dot and cross diagrams for covalentElectrons that are not shared must still be shown. They are normally arranged in lone pairs around their atom.
Do not omit lone pairs. Chlorine in HCl has three, oxygen in H₂O has two, and each oxygen in O₂ and CO₂ has two.
Put bonding pairs between the bonded atoms and include every unshared outer-shell electron as part of a lone pair.
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