chemcheat

PH3 Lewis Structure

Phosphine · A toxic gas used as a fumigant and in semiconductor manufacturing.

Lewis structure of PH3 (Phosphine)The individual bonds are close to nonpolar, but the lone pair sits on one side of the molecule, so there is still a net dipole.PHHH

The PH3 Lewis structure has 8 valence electrons, drawn as three bonds to hydrogen, with one lone pair in total. The central P is sp3 hybridized, which makes it a trigonal pyramidal molecule with a bond angle of 107 degrees. PH3 is polar: the individual bonds are close to nonpolar, but the lone pair sits on one side of the molecule, so there is still a net dipole.

Calculated properties

Calculated properties of PH3
Total valence electrons 8
Bonding electrons 6 (3 shared pairs)
Nonbonding electrons 2 (1 lone pairs)
Lone pairs on P 1
Electron domains (steric number) 4
VSEPR notation AX3E1
Electron geometry tetrahedral
Molecular geometry trigonal pyramidal
Bond angle 107°
Hybridization sp3
Polarity polar
Formal charges all zero
Resonance structures none
Molar mass 33.998 g/mol

How to draw the PH3 Lewis structure

  1. 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 (P) + 3 x 1 (H) = 8 valence electrons

  2. Choose the central atom

    P is the least electronegative atom here, so it takes the centre. Hydrogen is never central: it can only form one bond.

  3. 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.

    3 bonds x 2 = 6 electrons used, 2 left

  4. 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 2, has 2, exactly enough

  5. 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.

    P: 1 (2 electrons)

  6. Check the central atom

    P ends up with a full octet. Every electron in the budget is now placed.

    P: 6 bonding + 2 nonbonding = 8

  7. 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

  8. Work out the shape

    Count the electron domains on P: 3 bonded groups plus 1 lone pair. 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 trigonal pyramidal arrangement. One lone pair pushes the three bonds down from the ideal 109.5 degrees.

    steric number 4 -> sp3 -> trigonal pyramidal, bond angle 107

  9. Decide whether it is polar

    The individual bonds are close to nonpolar, but the lone pair sits on one side of the molecule, so there is still a net dipole.

    dipoles do not cancel -> polar

Is PH3 polar or nonpolar?

PH3 is polar. The individual bonds are close to nonpolar, but the lone pair sits on one side of the molecule, so there is still a net dipole.

BondElectronegativity differenceCharacter
P–H 0.01 nonpolar covalent
Why this molecule gets set as a problem: The bonds are almost nonpolar, but the lone pair still makes the molecule polar.

Common questions

How many valence electrons does PH3 have?

PH3 has 8 valence electrons. 6 of them are in bonds and 2 sit in lone pairs.

What is the molecular geometry of PH3?

PH3 is a trigonal pyramidal molecule. The central P has 3 bonded groups and one lone pair, a steric number of 4, which gives tetrahedral electron geometry and a trigonal pyramidal molecule.

What is the bond angle in PH3?

The bond angle in PH3 is 107 degrees. One lone pair pushes the three bonds down from the ideal 109.5 degrees.

What is the hybridization of PH3?

The central P in PH3 is sp3 hybridized. Steric number 4 means 4 orbitals have to be mixed, which is exactly what sp3 gives you.

Is PH3 polar or nonpolar?

PH3 is polar. The individual bonds are close to nonpolar, but the lone pair sits on one side of the molecule, so there is still a net dipole.

How this page was produced. The formula was parsed, the connectivity resolved (central atom), and every bond-order arrangement enumerated and scored on octet satisfaction, formal charge and where that charge sits. The structure above is the winner. Bond angles, hybridization and the polarity verdict are read off the resulting geometry, not looked up.