To help us with this example question, I decided to leave this periodic table up so we can see how to best use it. Here it says write the ground state electron configuration for the following element. Here we're dealing with fluorine and they tell us that it has an atomic number of nine, which means it has nine electrons.
On this periodic table, we find fluorine right here. Ground state means that we're going to start out with 1S orbital and work our way up to fluorine. So we're going to count to fluorine. So we'd say 1S2 1S2 2S2 because of 1/2 slots and then we have to count to F so that would be 2P5. We're in the 2P row. And how many slots do we have to count to get to fluorine? 1 2 3 4 5 2P5.
So here this would be the ground state electron configuration of the fluorine atom. And realize here that these are the number of electrons. So when you add them up 2 + 2 + 5, that gives me 9 electrons, which is related to the atomic number here of fluorine.
Remember, when an element is neutral, its atomic number tells us both the number of protons and the number of electrons. So again, rely on this depiction of the periodic table to help guide you to the right electron configuration of any element or ion given to you.