What is a covalent bond?
3 marks · NormalA molecule of ammonia () is formed by nitrogen bonding covalently with three hydrogen atoms.
Given that each covalent bond is formed by the sharing of one pair of electrons, calculate the total number of electrons that nitrogen shares with hydrogen in ammonia.
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6 electrons (±0)
Also accept: 6
Common mistakes: 3 electrons (counting just the number of bonds); 9 electrons (assuming triple bond between N and one H)
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Marking points
M1 · 1 mark · Identifies that each covalent bond involves a shared pair (2) of electrons.
M2 · 1 mark · Multiplies the number of covalent bonds (3) by 2 electrons per bond.
A1 · 1 mark · Arrives at the correct total: 6 electrons. (follow-through)
Worked solution
Each covalent bond is formed by the sharing of 2 electrons (a pair).
In , nitrogen forms 3 covalent bonds with 3 hydrogen atoms.
Therefore, nitrogen shares a total of 6 electrons with hydrogen in ammonia.