This is the CH3- Lewis structure.
On the periodic table, Carbon has 4 valence
electrons.
Hydrogen has 1, but we have three Hydrogens.
Then we have this negative up here so we need
to add an additional valence electron for
a total of 4 plus 3 plus 1: 8 valence electrons.
We'll put the Carbon in the center.
Hydrogen always goes on the outside.
We have three of them, just put them around
like this.
We'll put two valence electrons between the
Hydrogen and the Carbon in each case to form
chemical bonds.
We've used 2, 4, 6 valence electrons.
We have 8, so we'll put the remaining two
here on top of the Carbon.
Hydrogen only needs 2 valence electrons for
a full outer shell, and each Hydrogen in this
structure has two valence electrons.
Carbon needs 8 for an octet, and it has 8
as well.
If you calculate the formal charges for the
Carbon, you'll see that it's a negative one
formal charge on the Carbon.
The Hydrogens have a formal charge of zero.
And that negative makes sense because we have
a negative up here.
So this is the Lewis structure for CH3-.
This is Dr. B., and thanks for watching.
