H2S Lewis Structure
Hydrogen sulfide · The rotten-egg gas, produced by anaerobic decay and by oil refining.
The H2S Lewis structure has 8 valence electrons, drawn as two bonds to hydrogen, with two lone pairs in total. The central S is sp3 hybridized, which makes it a bent molecule with a bond angle of 104.5 degrees. H2S is polar: the individual bonds are close to nonpolar, but the lone pairs sit on one side of the molecule, so there is still a net dipole.
- 8 valence e−
- bent
- 104.5° bond angle
- sp3
- polar
Calculated properties
| Total valence electrons | 8 |
|---|---|
| Bonding electrons | 4 (2 shared pairs) |
| Nonbonding electrons | 4 (2 lone pairs) |
| Lone pairs on S | 2 |
| Electron domains (steric number) | 4 |
| VSEPR notation | AX2E2 |
| Electron geometry | tetrahedral |
| Molecular geometry | bent |
| Bond angle | 104.5° |
| Hybridization | sp3 |
| Polarity | polar |
| Formal charges | all zero |
| Resonance structures | none |
| Molar mass | 34.076 g/mol |
How to draw the H2S Lewis structure
Step through it. The bar shows how much of the 8-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. 2 bonds spends 4 electrons.
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Centre. Everything still unplaced goes on S, which now has 8 electrons around it.
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.
2 x 1 (H) + 6 (S) = 8 valence electrons -
Choose the central atom
S is the least electronegative atom here, so it takes the centre. Hydrogen is never central: it can only form one bond.
-
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.
2 bonds x 2 = 4 electrons used, 4 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 4, has 4, 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.
S: 2 (4 electrons) -
Check the central atom
S ends up with a full octet. Every electron in the budget is now placed.
S: 4 bonding + 4 nonbonding = 8 -
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 S: 2 bonded groups plus 2 lone pairs. A double or triple bond still counts as one domain, because it points in one direction. That gives tetrahedral electron geometry; ignore the lone pairs and the atoms themselves sit in a bent arrangement. Two lone pairs repel more strongly than bonding pairs, closing the angle well below 109.5 degrees.
steric number 4 -> sp3 -> bent, bond angle 104.5 -
Decide whether it is polar
The individual bonds are close to nonpolar, but the lone pairs sit on one side of the molecule, so there is still a net dipole.
dipoles do not cancel -> polar
Is H2S polar or nonpolar?
H2S is polar. The individual bonds are close to nonpolar, but the lone pairs sit on one side of the molecule, so there is still a net dipole.
| Bond | Electronegativity difference | Character |
|---|---|---|
| S–H | 0.38 | nonpolar covalent |
Common questions
How many valence electrons does H2S have?
H2S has 8 valence electrons. 4 of them are in bonds and 4 sit in lone pairs.
What is the molecular geometry of H2S?
H2S is a bent molecule. The central S has 2 bonded groups and two lone pairs, a steric number of 4, which gives tetrahedral electron geometry and a bent molecule.
What is the bond angle in H2S?
The bond angle in H2S is 104.5 degrees. Two lone pairs repel more strongly than bonding pairs, closing the angle well below 109.5 degrees.
What is the hybridization of H2S?
The central S in H2S is sp3 hybridized. Steric number 4 means 4 orbitals have to be mixed, which is exactly what sp3 gives you.
Is H2S polar or nonpolar?
H2S is polar. The individual bonds are close to nonpolar, but the lone pairs sit on one side of the molecule, so there is still a net dipole.