00:01
So when we're thinking about whether substances will gain or lose electrons, we need to know how many valence electrons they have.
00:09
Remember, the most elements would like eight electrons to fill their valence shell.
00:15
And so you have to think how close you are to eight.
00:18
If you're very close to eight, you're going to gain electrons to make eight.
00:24
If you're not very close to eight, if you have like one or two or three, you're more likely to lose.
00:30
Lose electrons in order to get the shell below to be your outermost full shell.
00:39
So in green, i have the number of valence electrons that atoms have as neutral elements.
00:48
And then based on that, if we lose one electron, we would have a plus one charge.
00:52
If we lose two electrons, we'd have a plus two charge, et cetera.
00:56
But if we get closer to eight, say we have five, we will instead, gain three electrons.
01:02
Electrons are negative, so to have a charge of negative three, et cetera.
01:06
So based on where these elements are on the periodic table, we can figure out how many valence electrons there are, and then figure out whether they would gain or lose electrons and how many in order to get to their ions.
01:19
So the first case, we have radium, ra.
01:25
So we're going to find ra down here in the second column has two valence electrons.
01:32
It'll get rid of two.
01:34
So radium will have a plus two charge...