Drawing the Lewis Structure for PH3

Viewing Notes:

  • The Lewis structure for PH3 is similar to NH3.
  • In the PH3 Lewis structure (and all Lewis structures) hydrogen goes on the outside. Remember, too, that hydrogen only needs two valence electrons to have a full outer shell.
  • In the Lewis structure for PH3 there are a total of 8 valence electrons. Three pairs will be used in the chemical bonds between the P and H and one pair of electrons will be unbonded.

Transcript: Hi, this is Dr. B. Let's do the PH3 Lewis structure. On the periodic table: Phosphorus, group 5, 5 valence electrons; Hydrogen, group 1, but we have three of them for a total of 8 valence electrons. We'll take and put the Phosphorus in the center. Hydrogens always go on the outside. We have 3 of them. We'll put 2 electrons between each of the atoms to form chemical bonds. We've used 6 valence electrons. Put the last two in the center for a total of 8 valence electrons.

So we've used all 8 valence electrons. Hydrogen has 2, this Hydrogen has 2, as does this, so all the Hydrogens are OK since they only need 2 valence electrons for a full outer shell. Then the Phosphorus in the center has 8, so it has a full shell.

That's the Lewis structure for PH3. This is Dr. B., and thanks for watching.