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ScienceQuest

Hydrazine (N₂H₄) Lewis structure

14 valence electrons, trigonal pyramidal

N N H H H H
N₂H₄ as the Lewis Structure Generator draws it: lone pairs as dots.

Build N₂H₄ step by step in the Lewis Structure Generator

What is the Lewis structure of N₂H₄?

Hydrazine, N₂H₄, has 14 valence electrons. The two N atoms bond to each other, and the molecule has one N−N single bond and four N−H single bonds. It carries one lone pair on each central N. Every formal charge is zero. Each N is AX₃E₁: trigonal pyramidal, with an ideal bond angle of 109.5°.

Valence electrons in N₂H₄

Element Group Valence electrons Atoms Electrons
Nitrogen 15 5 2 10
Hydrogen 1 1 4 4
Total 14

In one line: 2 × 5 + 4 × 1 = 14. Each atom brings the valence electrons its group gives it.

How to draw the N₂H₄ Lewis structure

  1. Count the valence electrons. Valence electrons: each N 5 and each H 1. 2 × 5 + 4 × 1 = 14.
  2. Bond the two central atoms. N appears twice, so the two N atoms bond to each other and share the H atoms evenly between them.
  3. Join the atoms with single bonds. Five single bonds use 10 electrons, leaving 14 − 10 = 4.
  4. Complete the outer atoms. Every outer atom is H, and its one bond already gives it the two electrons it holds. 4 remain.
  5. Put the rest on the central atom. The 4 left go on the central atoms as one lone pair on each N, and each N now has 8 electrons round it.
  6. Make multiple bonds where needed. Every atom already has an octet, so no lone pair needs to become a bond.

Lone pairs and formal charges in N₂H₄

Atom Number Bonds Lone pairs Electrons round it Formal charge, V − N − B/2
N (central) 2 three single bonds 1 8 5 − 2 − 3 = 0
H 4 one single bond 0 2 1 − 0 − 1 = 0

V is the atom’s valence electrons, N its nonbonding electrons and B its bonding electrons. The formal charges add up to 0, the molecule’s overall charge.

Shape and polarity of N₂H₄

Central atoms each N
VSEPR class AX₃E₁
Electron geometry tetrahedral
Molecular geometry trigonal pyramidal
Ideal bond angle 109.5°
Polarity, an estimate depends

It depends on the twist about the central bond, which a Lewis structure does not fix. H₂O₂ and N₂H₄ are both polar in practice.

Each N has three σ bonds and one lone pair, four electron domains in all, so its electron geometry is tetrahedral. Counting only the bonded atoms, the molecular geometry is trigonal pyramidal.

The VSEPR Molecular Geometry viewer turns the AX₃E₁ shape in 3D, lone pairs included.

Work with N₂H₄