SeF6 Lewis Structure
Selenium hexafluoride · A toxic colourless gas, the selenium analogue of sulfur hexafluoride.
The SeF6 Lewis structure has 48 valence electrons, drawn as six Se–F bonds, with 18 lone pairs in total. The central Se is sp3d2 hybridized, which makes it an octahedral molecule with a bond angle of 90 degrees. SeF6 is nonpolar: the bond dipoles are all the same size and the shape places them symmetrically around the central Se, so they cancel exactly.
- 48 valence e−
- octahedral
- 90° bond angle
- sp3d2
- nonpolar
SeF6 molecular geometry
Octahedral, from 6 electron domains on the central Se: 6 bonded atoms (AX6). The electron geometry is octahedral. Wedges point toward you, hashed wedges away. Every shape in the VSEPR chart →
Calculated properties
| Total valence electrons | 48 |
|---|---|
| Bonding electrons | 12 (6 shared pairs) |
| Nonbonding electrons | 36 (18 lone pairs) |
| Lone pairs on Se | 0 |
| Electron domains (steric number) | 6 |
| VSEPR notation | AX6 |
| Electron geometry | octahedral |
| Molecular geometry | octahedral |
| Bond angle | 90° |
| Hybridization | sp3d2 |
| Polarity | nonpolar |
| Formal charges | all zero |
| Resonance structures | none |
| Molar mass | 192.959 g/mol |
Se Selenium 6 valence e− F Fluorine 6 atoms, 7 valence e− each
How to draw the SeF6 Lewis structure
Step through it. The bar shows how much of the 48-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. 6 bonds spends 12 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.
6 (Se) + 6 x 7 (F) = 48 valence electrons -
Choose the central atom
Se 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.
6 bonds x 2 = 12 electrons used, 36 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 36, has 36, 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, F6: 3 (36 electrons) -
Check the central atom
Se ends up with 12 electrons, an expanded octet. Only period 3 and below can do this.
Se: 12 bonding + 0 nonbonding = 12 -
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 Se: 6 bonded groups. A double or triple bond still counts as one domain, because it points in one direction. That gives octahedral electron geometry; ignore the lone pairs and the atoms themselves sit in a octahedral arrangement.
steric number 6 -> sp3d2 -> octahedral, bond angle 90 -
Decide whether it is polar
The bond dipoles are all the same size and the shape places them symmetrically around the central Se, so they cancel exactly.
dipoles cancel -> nonpolar
Is SeF6 polar or nonpolar?
SeF6 is nonpolar. The bond dipoles are all the same size and the shape places them symmetrically around the central Se, so they cancel exactly.
| Bond | Electronegativity difference | Character |
|---|---|---|
| Se–F | 1.43 | polar covalent |
Common questions
How many valence electrons does SeF6 have?
SeF6 has 48 valence electrons. 12 of them are in bonds and 36 sit in lone pairs.
What is the molecular geometry of SeF6?
SeF6 is an octahedral molecule. The central Se has 6 bonded groups, a steric number of 6, which gives octahedral electron geometry and an octahedral molecule.
What is the bond angle in SeF6?
The bond angle in SeF6 is 90 degrees. That is the ideal octahedral angle, and nothing distorts it here.
What is the hybridization of SeF6?
The central Se in SeF6 is sp3d2 hybridized. Steric number 6 means 6 orbitals have to be mixed, which is exactly what sp3d2 gives you.
Is SeF6 polar or nonpolar?
SeF6 is nonpolar. The bond dipoles are all the same size and the shape places them symmetrically around the central Se, so they cancel exactly.
Why does SeF6 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.