00:03
There, in this question, we are writing ionic compounds.
00:07
And ionic compounds are composed of a cation and an ion.
00:19
The cation is positively charged, and the anionion is negatively charged.
00:28
Ionic compounds are neutral.
00:32
That means the total positive and negative charges have to add up to zero.
00:53
Okay, so the total positive and negative charge have to add to zero, and we'll accomplish this by adding subscripts as necessary when we're writing these.
01:01
All right, so let's go ahead and put these together.
01:05
First thing we want to do is write the cation and the anion with their appropriate charges, and then write the chemical formula.
01:13
So magnesium, that is in group 2a of the periodic table.
01:17
All of the elements in group 2a form ions with a 2 plus charge when they lose their two valence electrons.
01:24
Oxygen is group 6a, therefore, or it has, when it forms an ion, the ion has a two -negative charge.
01:33
The compound it forms is magnesium oxide, which is simply going to be mgo because two positive and two -negative already add up to zero.
01:45
All right.
01:45
For letter b, we have ribidium bromide.
01:50
Rubidium is rb.
01:52
It's in group 1a of the periodic table, so it has a single positive charge.
01:57
Bromide, that's a halogen.
01:59
It's in group 7a.
02:01
Halogens, when they form ions, they form ions with a single charge, a single negative charge.
02:07
So positive 1, negative 1, already add to 0.
02:11
So this is simply rb, br.
02:20
Looking at letter c.
02:25
In letter c, we have strontium iodide.
02:27
Stronium is back in group 2a of the periodic table, and we know all of those form ions with a 2 plus charge.
02:35
Iodide is a halogen.
02:37
That means to be.
02:37
Just a single negative charge...