Lewis structure

Lewis structure of HNO₃

24 valence electrons. One N=O double bond, one N-O single bond and one N-OH single bond, with no lone pair on N.

Molecule or ion

HNO₃Nitric acid

Trigonal planar

AB₃: 3 bond pairs, no lone pairs

24 valence electrons

i

As in NCERT Table 4.1: N carries +1 and the single bonded O carries -1.

Formal charges: N +1, O −1

N has 5 valence electrons. In the Lewis structure it makes one double bond to O and two single bonds to O and keeps no lone pair, which leaves it a formal charge of +1.
Steric number = three sigma bonds + no lone pairs = 3, so N is sp² hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.
Three electron pairs point to the corners of a flat triangle (trigonal planar electron geometry). With no lone pairs the atoms take the same shape: trigonal planar.
There is no lone pair on N, but the three N-O bonds are not alike (a double bond, a single bond and N-OH), so the angles are near 120 degrees, not all equal.
The bond dipoles do not cancel in the trigonal planar shape, so HNO₃ is polar.

Working

How to draw it

Count the valence electrons: N 5 + 3 × O 6 + H 1 = 24 valence electrons, 12 pairs.
Put N in the middle and join it to the three outer atoms with single bonds.
Give each outer atom lone pairs until it has an octet (H needs only two electrons), then put any electrons left over on the central atom.
Where an atom is still short of an octet, turn a lone pair of its neighbour into a shared pair: that makes a double or triple bond.
Result: one N=O double bond, one N-O single bond and one N-OH single bond, with no lone pair on N.
Formal charge = valence electrons − lone pair electrons − number of bonds. Here: N +1, O −1.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

How many valence electrons are in HNO3?

N 5 + 3 × O 6 + H 1 = 24 valence electrons, 12 pairs.

What are the formal charges in the Lewis structure of HNO3?

N +1, O −1; every other atom is zero. Formal charge = valence electrons - lone pair electrons - number of bonds.

How many lone pairs are in the Lewis structure of HNO3?

7 in all, none on the central N.