00:01
In this question we're going to be looking into the number of valence electrons.
00:06
So by the valence electrons we are looking at the outer most shell electrons.
00:13
So let's just look at the first one where we've been given helium.
00:17
If we are to look at helium, the electronic configuration of helium, this is 1s2.
00:24
So if we look at this, we have only one shell and one orbital which is the s orbital.
00:30
So just looking at the number of outermost shell electrons, we have just two electrons.
00:37
This is simply enough because we have only one shell.
00:41
So we're just looking at that shell being the phallens shell.
00:45
Looking at another one, let's just look at n3 minus.
00:49
Before we look at n3 minus, let's just look at a neutral nitrogen atom whose electronic configuration is given by 1s2, 2s2 and 2p3.
00:59
Now if we look at this, the number of shells here that we have is just two shells.
01:05
And although in two shells we might have two types of orbitals, but it does not nucleate the fact that we only have the total of n equal to 2, that is, two shells.
01:16
So the valence shell electrons in nitrogen atom is we have 5 electrons.
01:22
But then we are looking at n3 minus the iron.
01:26
What happened is we added three electrons into a nitrogen neutral nitrogen atom to form this n3 minus ion and those electrons are going to into the highest energy orbital that is the outermost shell orbital and that orbital is the 2p3 orbital so what we're going to have is 2 s2 and 2p6 now looking at this the total number or of shells is still equal to 2, but the number of electrons in the outermost shell, it is not 6, but it is equal to 8, because we are looking at the outermost shell, not necessarily the orbitals.
02:12
The number of shells that we have here is 1 and 2, and the outermost shell is shell number 2.
02:19
And in it we have 2 orbitals, the s orbitals and the p orbitals.
02:23
And combining the total number of electrons in a shell in n3 minus this is going to be two electrons in the os orbital and six electrons in the p orbitals to give us a total of eight valence electrons now if we are to just draw the structure the lowest structure we are going to have a total of eight orbitals and the same applies to helium where we just have two just have two electrons two valence electrons now another thing to simplify this question we know that the group number gives us the number of valence electrons that is for example for nitrogen nitrogen is in group five so it has a total of five valence electrons and this is in line with what we can see in the electronic configuration we have two plus three electrons that are coming from s orbital and p orbitals which are in a second shell.
03:27
So the total number of electrons indeed corresponds to the group number, which is in this case for nitrogen is going to be equal to five...