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ScienceQuest

Hydrogen fluoride (HF) Lewis structure

8 valence electrons, linear

H F
HF as the Lewis Structure Generator draws it: lone pairs as dots.

Build HF step by step in the Lewis Structure Generator

What is the Lewis structure of HF?

Hydrogen fluoride, HF, has 8 valence electrons. Its two atoms are joined by one H−F single bond. It carries three lone pairs on the F. Every formal charge is zero. As two atoms it is linear, and the molecule is polar.

Valence electrons in HF

Element Group Valence electrons Atoms Electrons
Hydrogen 1 1 1 1
Fluorine 17 7 1 7
Total 8

In one line: 1 + 7 = 8. Each atom brings the valence electrons its group gives it.

How to draw the HF Lewis structure

  1. Count the valence electrons. Valence electrons: H 1 and F 7. 1 + 7 = 8.
  2. Join the two atoms. With only two atoms there is no choice to make: they bond to each other.
  3. Join the atoms with single bonds. One single bond uses 2 electrons, leaving 8 − 2 = 6.
  4. Complete the outer atoms. Every outer atom is H, and its one bond already gives it the two electrons it holds. 6 remain.
  5. Put the rest on F. The 6 left go as three lone pairs on F, and F 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 HF

Atom Number Bonds Lone pairs Electrons round it Formal charge, V − N − B/2
H 1 one single bond 0 2 1 − 0 − 1 = 0
F 1 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 HF

Central atom none, two atoms
Electron geometry linear
Molecular geometry linear
Ideal bond angle none, two atoms
Polarity, an estimate polar

The electronegativities differ by 1.78, so the shared electrons sit nearer F.

Work with HF