00:02
Hi there.
00:03
In this question, we actually have three questions where we are identifying atoms or electrons.
00:10
I'm sorry, atoms or ions.
00:12
So letter a, we are told it's an anion.
00:16
So anion tells us it's a negative ion, which means it has gained one or more electrons.
00:29
All right.
00:30
And we're told that it has 54 electrons.
00:37
And we're told it's a halogen.
00:39
So the halogens are group 7.
00:41
So we're told it is a halogen and it has 54 electrons.
00:46
Well halogens have seven valence electrons of their own since they're in group seven.
00:51
So to form an ion, this one must have gained one electron.
00:57
So if we subtract one electron from this, we get 53 electrons.
01:06
So the neutral atom has 53 electrons.
01:09
Since the ion had 54, the neutral atom has 53.
01:19
And if it has 53 electrons and it's neutral, it also has 53 protons.
01:26
And the protons tell us the atomic number.
01:30
So that means we're looking for the element that has atomic number 53.
01:34
So this ion is the halogen iodine, and it has a one negative charge, because halogens, gain that one electron to form an ion.
01:48
So this is the iodide ion.
01:51
All right, let's move on to letter b.
01:54
Letter b wants a metal cation.
01:56
So it's a metal.
01:57
It's a cation, which means a positive ion.
02:00
So it has lost electrons.
02:03
It has 79 protons and 76 electrons.
02:12
So it has three more positive charges than negative charges, telling us it's going to have a three positive charge and since it has 79 protons, that means it is atomic number 79.
02:25
Atomic number 79 is gold.
02:31
Therefore, this is going to be gold, and since it has three fewer electrons, it forms a cation with that three positive charge.
02:42
All right, so the answer for this then is au with a three positive charge.
02:49
Let's look next at letter c.
02:53
Letters c, we have a noble gas...