Here we need to determine the number of the electron highlighted within the electron orbital diagram. So if we look this is what 1S22S22P63S23P4 and we're looking at this electron. Here, we have to determine its number. All right, so we number it in the order of the off file principle.
So we start out with 1S2, so we start numbering them first. So one up, SO11 down to one up, three one down 4. Now 2P6. These are degenerate orbitals, They have the same energy. So following Hun's role we have build them first. So this would be up, up, up. So I number them 567. Then we came back around 8910.
Now we're at 3's again, so 1112, three P orbitals, they're degenerate, same energy again, so half fill according to Hun's rule 13141516. And we can see here that this electron that's highlighted is the 14th electron. So remember, that's the way we're able to number the electrons within an electron orbital diagram. This is key for later on connecting it to the quantum numbers.