Skip to content
ScienceQuest

Dibromocarbene (CBr₂) Lewis structure

18 valence electrons, bent

C Br Br
CBr₂ as the Lewis Structure Generator draws it: lone pairs as dots.

Build CBr₂ step by step in the Lewis Structure Generator

What is the Lewis structure of CBr₂?

Dibromocarbene, CBr₂, has 18 valence electrons. Carbon is the central atom, joined by two C−Br single bonds. It carries one lone pair on the central C and three on each Br. Every formal charge is zero. C is AX₂E₁: bent, with an ideal bond angle of 120°, and the molecule is polar.

Valence electrons in CBr₂

Element Group Valence electrons Atoms Electrons
Carbon 14 4 1 4
Bromine 17 7 2 14
Total 18

In one line: 4 + 2 × 7 = 18. Each atom brings the valence electrons its group gives it.

How to draw the CBr₂ Lewis structure

  1. Count the valence electrons. Valence electrons: C 4 and each Br 7. 4 + 2 × 7 = 18.
  2. Choose the central atom. C goes in the middle: C is the least electronegative atom other than H, χ 2.55 against 2.96 for Br.
  3. Join the atoms with single bonds. Two single bonds use 4 electrons, leaving 18 − 4 = 14.
  4. Complete the outer atoms. Each outer atom takes enough lone pairs to reach eight: 2 Br × 6 = 12, leaving 14 − 12 = 2.
  5. Put the rest on the central atom. The 2 left go on the central atom as one lone pair on C, and C now has 6 electrons round it.
  6. Make multiple bonds where needed. C is left with 6 electrons. A double bond from an outer atom would complete its octet only by putting positive charge on the more electronegative atom, so C stays short, one of the known exceptions to the octet rule.

Lone pairs and formal charges in CBr₂

Atom Number Bonds Lone pairs Electrons round it Formal charge, V − N − B/2
C (central) 1 two single bonds 1 6 4 − 2 − 2 = 0
Br 2 one single bond 3 8 7 − 6 − 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 CBr₂

Central atom C
VSEPR class AX₂E₁
Electron geometry trigonal planar
Molecular geometry bent
Ideal bond angle 120°
Polarity, an estimate polar

The bent shape leaves the bond dipoles unbalanced.

C has two σ bonds and one lone pair, three electron domains in all, so its electron geometry is trigonal planar. Counting only the bonded atoms, the molecular geometry is bent.

The VSEPR Molecular Geometry viewer turns the AX₂E₁ shape in 3D, lone pairs included.

Notes on the CBr₂ Lewis structure

Work with CBr₂