Numford
Hybridisation

Hybridisation of NO₃⁻

N is sp² hybridised (hybridization by the VSEPR count): 3 sigma bonds and no lone pairs give a trigonal planar shape, bond angle 120°.

ONOO
  • N
  • O

NO₃⁻Nitrate ion

Trigonal planar

AB₃: 3 bond pairs, no lone pairs

  • Hybridisationsp²
  • Bond angle120°
  • Polarityion, charge −1

Why this shape

  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.
  2. 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.
  3. 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.
  4. All the bond pairs repel each other equally, so the angle is the ideal 120°.
  5. NO₃⁻ is an ion with an overall charge of −1, so it is not described as polar or non-polar.

Lewis structure

24 valence electrons, 3 resonance structures
i

The double bond is shared by all three O atoms, so all three N-O bonds are the same length.

NOOO+−−
NOOO+−−
NOOO+−−

Formal charges: N +1, O −1 on two atoms

Working

Why this hybridisation and shape

  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.
  2. 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.
  3. 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.
  4. All the bond pairs repel each other equally, so the angle is the ideal 120°.
  5. NO₃⁻ is an ion with an overall charge of −1, so it is not described as polar or non-polar.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Hybridisation of NO3-: quick answers

What is the hybridisation of NO3-?

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.

What is the shape of NO3- and its bond angle?

Trigonal planar, with a bond angle of 120 degrees. 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. All the bond pairs repel each other equally, so the angle is the ideal 120°.

How many lone pairs are on the central atom of NO3-?

None. 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.

Try any molecule