Build the HNO3 Molecule
Double, single, and a coordinate bond give nitrogen its valency of 5
What this lesson covers
Why it matters
Nitric acid is a powerful oxidiser, and its structure hides neat logic: nitrogen uses all five of its outer electrons — one in the N–OH bond, two in the N=O double bond, and two in the N→O coordinate bond, where nitrogen donates the whole pair. 1 + 2 + 2 = 5.
Predict first
How does nitrogen use its five valence electrons in a stable HNO₃ molecule?
In nitric acid nitrogen shows valency 5: a single bond to the OH group, a double bond to one oxygen, and its whole lone pair donated to the third oxygen as a coordinate bond.
- Only three form bonds; two stay back as a free lone pair
- All five are engaged: one in the N–OH bond, two in the N=O double bond, and the lone pair donated as a coordinate bond — correct
- Four bonds, exactly like carbon in organic acids
- Two bonds, to keep the molecule neutral
What you do
Build nitric acid (HNO₃): give nitrogen a double bond to one oxygen, a single bond to the –OH oxygen, and donate a lone pair to the third oxygen as a coordinate bond (→) — together they give nitrogen a valency of 5.
Check yourself
Which structural feature correctly describes the bonding in HNO3?
HNO₃ has one H, one N and three O in total: the nitrogen carries one –OH group, one double-bonded O, and one O held by a coordinate bond.
Why does nitrogen show a valency of 5 in nitric acid?
Nitrogen's 2,5 configuration gives five outer electrons, and in HNO₃ all five are engaged in bonding — which is what 'valency 5' means here.
- Nitrogen is bonded to three hydrogens
- Nitrogen is bonded to two oxygen atoms and one hydroxyl (–OH) group — correct
- Nitrogen is bonded to only two oxygens
- All five valence electrons take part — three shared in single and double bonds plus the donated lone pair — correct
- Because it has 5 protons
- To repel the hydrogen atom