If you have been reading them all, you should be excited to know that zinc is the last transition element in the fourth period on the table of elements. Zinc’s location reflects the fact that is has a completely filled third electron shell. The configuration of 2-8-18-2 also lets you know that elements are about to change dramatically as you move to the right.

The element gallium begins to add electrons to the fourth shell and acts more like aluminum and boron, not cadmium and mercury. Finishing your look at the electron configuration, you need to remember that the outer shell still only has two electrons even though the row of transition elements has filled in an additional ten electrons to the third shell.