This is Dr. B.  Let's do the I3- Lewis structure.
On the periodic table, Iodine is in group 7 or
17. It has seven valence electrons.
But we have three of them (Iodine atoms).
And then we have this negative up here. So we're going to add another electron to that:
so 21 plus 1, 22 total valence electrons
so will put our Iodines in lines like
this
and then we're gonna put electrons
between each of the atoms to form
chemical bonds.
Put a pair here, here, here
and now around atoms.
So we used 2, 4, 6, 8, 10,
12, 14, 16,
so we have six left over and we'll just
have to put them on the Iodine right
here like this.
so we've used all 22 of the
valence electrons that we had available
and it's kind of strange structure so
let's check or formal charges just to
make sure that we have the best Lewis Structure for I3-.
So the two Iodines on the outside, the ones in
green, let's do those first. They're the same so
they'll have the same formal charge. On
the periodic table Iodine is in group seven;
seven valence electrons. Non-bonding,
these right here that are not involved
in chemical bonds, we have six
and then bonding
we have two but we'll divide that by two. Seven
minus six minus one gives us zero.
For the Iodine in the middle, the blue
Iodine, seven valence electrons for
iodine
we have six non-bonding, so these four up
here aren't bonding and these two down
here so six non-bonding valence
electrons
and then we have two plus two, four bonding valence electrons which will divide by
two. Seven minus six minus two gives us a
negative one charge
So all of this makes sense. We have the
negative one charge here. That
makes sense: we have a negative three so
we can draw this with brackets so
everyone can see that it is an ion.
Put a negative up there.
That's the lewis structure for I3-
This is Dr. B,
and thanks for watching.
