Hi this is Dr. B. we're gonna do the
Lewis structure for CH4, methane.
Cows make a lot a methane. We'll
first take a look at the periodic table.
Carbon is in group four or fourteen so it
has four valence electrons.
Hydrogen, group one, has one valence
electron. So we have 4 for Carbon plus one
but we have four
Hydrogens so let's multiply that by four.  
right there
so four plus 1 times 4;
8 valence electrons for us to work with
here.
We'll take and put carbon right here.
Hydrogen always goes on the outside
and we have 4 of them.
Put those on the outside and now we have
8 valence electrons to work with so let's
take those and form bonds between the Carbon and the Hydrogen.
Put a pair of electrons there and we have
8 valence electrons: so 2,
4
6 ... 8.
So we formed those chemical bonds
Hydrogen and Carbon and we used
the valence electrons up.
Let's see...
we used 8 around the carbon so that's good
Hydrogen only needs two for a full outer
shell and that Hydrogen is good.
So we've done it. That's the Lewis
structure for CH4: methane.
We could write it as a structural formula
and that would look like this
right here where the single lines
represent
a pair of bonding electrons.
This is Dr. B.,
and thanks for watching.
