00:01
The number of protons that something has is designated by its symbol.
00:06
So if we have barium, for instance, barium is going to wind up having, if we look at the atomic number, 56 protons.
00:18
Now, in a neutral atom, it would have the same number of electrons, but these are not neutral.
00:23
This has a plus two charge.
00:26
And so that means that overall there's two more protons than a electron.
00:31
Electrons.
00:32
So we have to subtract two from the number of protons.
00:36
This has 54 electrons.
00:39
56 positive things plus 54 negative things equals the charge.
00:51
That's a good way to double check.
00:53
When we look at zinc with a charge of plus two, we can go to the periodic table.
00:57
Zinc is number 30.
00:59
So it has 30 protons.
01:01
Plus two means we have two fewer electrons.
01:05
Electrons.
01:07
You can double check.
01:08
30 minus 28 is 2.
01:12
Now we have the nitride ion, n3 minus, and is seven on the periodic table, so it has seven protons.
01:21
Now this is negative three...