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Hi, this is Dr. B. Let's do the Lewis structure for PCl3. Phosphorus, on the periodic table,
is in group 5, it has 5 valence electrons. Chlorine, group 7, but we have three of those
so we have 5 plus 7 (times 3 is 21) is 26 valence electrons. We'll put the Phosphorus
in the center and then we'll put the Chlorines around it, just like that. We'll put a pair
of electrons between each Chlorine and Phosphorus to form a chemical bond. We've used 6; so
we have 6, 8, 10, and 24. We have two more left over, but we need to have two around
the Phosphorus to give it an octet, so we'll put those on the central atom. Twenty-six
valence electrons. So all of the Chlorines have 8 valence electrons. They have octets,
and their outer shells are full. And the Phosphorus has 8 valence electrons, so it has an octet.
We've used all 26 valence electrons, everything has octets: so this is the Lewis structure
for PCl3. This is Dr. B., and thanks for watching.