AsF5 Lewis Structure
Arsenic pentafluoride · A strong Lewis acid and a toxic gas.
The AsF5 Lewis structure has 40 valence electrons, drawn as five As–F bonds, with 15 lone pairs in total. The central As is sp3d hybridized, which makes it a trigonal bipyramidal molecule with a bond angle of 90 and 120 degrees. AsF5 is nonpolar: the bond dipoles are all the same size and the shape places them symmetrically around the central As, so they cancel exactly.
- 40 valence e−
- trigonal bipyramidal
- 90° and 120° bond angle
- sp3d
- nonpolar
AsF5 molecular geometry
Trigonal bipyramidal, from 5 electron domains on the central As: 5 bonded atoms (AX5). The electron geometry is trigonal bipyramidal. Wedges point toward you, hashed wedges away. Every shape in the VSEPR chart →
Calculated properties
| Total valence electrons | 40 |
|---|---|
| Bonding electrons | 10 (5 shared pairs) |
| Nonbonding electrons | 30 (15 lone pairs) |
| Lone pairs on As | 0 |
| Electron domains (steric number) | 5 |
| VSEPR notation | AX5 |
| Electron geometry | trigonal bipyramidal |
| Molecular geometry | trigonal bipyramidal |
| Bond angle | 90° and 120° |
| Hybridization | sp3d |
| Polarity | nonpolar |
| Formal charges | all zero |
| Resonance structures | none |
| Molar mass | 169.912 g/mol |
As Arsenic 5 valence e− F Fluorine 5 atoms, 7 valence e− each
How to draw the AsF5 Lewis structure
Step through it. The bar shows how much of the 40-electron budget is spent at each stage - it never grows, which is the whole constraint.
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Skeleton. Join every connected pair with one bond. 5 bonds spends 10 electrons.
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Outer octets. Spend electrons as lone pairs on the outer atoms. That uses the entire budget, and the central atom has nothing left over.
The reasoning at each step
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Count the valence electrons
Add up the outer-shell electrons every atom brings. That total is the budget for the whole structure - every line and every dot has to come out of it, and nothing may be added.
5 (As) + 5 x 7 (F) = 40 valence electrons -
Choose the central atom
As is the least electronegative atom here, so it takes the centre. Hydrogen is never central: it can only form one bond.
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Join everything with single bonds first
Every connection starts as one shared pair. Draw them all before worrying about double bonds - the arithmetic in the next step is what tells you where the double bonds have to go.
5 bonds x 2 = 10 electrons used, 30 left -
Work out how far short you are
Add up what every atom still needs to fill its shell - eight electrons for most atoms, two for hydrogen - minus what its single bonds already give it. Compare that with the electrons you have left. The difference decides everything that follows.
needs 30, has 30, exactly enough -
Fill in the lone pairs
Every electron not in a bond sits as a lone pair on an atom. Each atom takes exactly what it needs to finish its shell - there is no choice left at this point.
F1: 3, F2: 3, F3: 3, F4: 3, F5: 3 (30 electrons) -
Check the central atom
As ends up with 10 electrons, an expanded octet. Only period 3 and below can do this.
As: 10 bonding + 0 nonbonding = 10 -
Check the formal charges
Formal charge is valence electrons, minus lone-pair electrons, minus the number of bonds. Every atom here comes out at zero, which is the sign of a good structure.
all formal charges = 0 -
Work out the shape
Count the electron domains on As: 5 bonded groups. A double or triple bond still counts as one domain, because it points in one direction. That gives trigonal bipyramidal electron geometry; ignore the lone pairs and the atoms themselves sit in a trigonal bipyramidal arrangement.
steric number 5 -> sp3d -> trigonal bipyramidal, bond angle 90 and 120 -
Decide whether it is polar
The bond dipoles are all the same size and the shape places them symmetrically around the central As, so they cancel exactly.
dipoles cancel -> nonpolar
Is AsF5 polar or nonpolar?
AsF5 is nonpolar. The bond dipoles are all the same size and the shape places them symmetrically around the central As, so they cancel exactly.
| Bond | Electronegativity difference | Character |
|---|---|---|
| As–F | 1.80 | largely ionic |
Common questions
How many valence electrons does AsF5 have?
AsF5 has 40 valence electrons. 10 of them are in bonds and 30 sit in lone pairs.
What is the molecular geometry of AsF5?
AsF5 is a trigonal bipyramidal molecule. The central As has 5 bonded groups, a steric number of 5, which gives trigonal bipyramidal electron geometry and a trigonal bipyramidal molecule.
What is the bond angle in AsF5?
The bond angle in AsF5 is 90 and 120 degrees. That is the ideal trigonal bipyramidal angle, and nothing distorts it here.
What is the hybridization of AsF5?
The central As in AsF5 is sp3d hybridized. Steric number 5 means 5 orbitals have to be mixed, which is exactly what sp3d gives you.
Is AsF5 polar or nonpolar?
AsF5 is nonpolar. The bond dipoles are all the same size and the shape places them symmetrically around the central As, so they cancel exactly.
Why does AsF5 break the octet rule?
The central atom has more than four bonded groups, so it has to hold more than eight electrons. Elements from period 3 downward can do this; period-2 elements like carbon, nitrogen and oxygen cannot.