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.
