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Bromine pentafluoride (BrF₅) Lewis structure

42 valence electrons, square pyramidal

Br F F F F F
BrF₅ as the Lewis Structure Generator draws it: lone pairs as dots.

Build BrF₅ step by step in the Lewis Structure Generator

What is the Lewis structure of BrF₅?

Bromine pentafluoride, BrF₅, has 42 valence electrons. Bromine is the central atom, joined by five Br−F single bonds. It carries one lone pair on the central Br and three on each F. Every formal charge is zero. Br is AX₅E₁: square pyramidal, with ideal bond angles of 90° and 180°, and the molecule is polar.

Valence electrons in BrF₅

Element Group Valence electrons Atoms Electrons
Bromine 17 7 1 7
Fluorine 17 7 5 35
Total 42

In one line: 7 + 5 × 7 = 42. Each atom brings the valence electrons its group gives it.

How to draw the BrF₅ Lewis structure

  1. Count the valence electrons. Valence electrons: Br 7 and each F 7. 7 + 5 × 7 = 42.
  2. Choose the central atom. Br goes in the middle: Br is the least electronegative atom other than H, χ 2.96 against 3.98 for F.
  3. Join the atoms with single bonds. Five single bonds use 10 electrons, leaving 42 − 10 = 32.
  4. Complete the outer atoms. Each outer atom takes enough lone pairs to reach eight: 5 F × 6 = 30, leaving 32 − 30 = 2.
  5. Put the rest on the central atom. The 2 left go on the central atom as one lone pair on Br, and Br now has 12 electrons round it. That is more than eight, which an atom from period 3 on can hold.
  6. Make multiple bonds where needed. Every atom already has an octet or more, so no lone pair needs to become a bond.

Lone pairs and formal charges in BrF₅

Atom Number Bonds Lone pairs Electrons round it Formal charge, V − N − B/2
Br (central) 1 five single bonds 1 12 7 − 2 − 5 = 0
F 5 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 BrF₅

Central atom Br
VSEPR class AX₅E₁
Electron geometry octahedral
Molecular geometry square pyramidal
Ideal bond angles 90° and 180°
Measured bond angle 84.8°
Polarity, an estimate polar

The square pyramidal shape leaves the bond dipoles unbalanced.

Br has five σ bonds and one lone pair, six electron domains in all, so its electron geometry is octahedral. Counting only the bonded atoms, the molecular geometry is square pyramidal.

The VSEPR Molecular Geometry viewer turns the AX₅E₁ shape in 3D, lone pairs included.

The measured angle is the accepted experimental value the VSEPR viewer quotes for this molecule.

Work with BrF₅