The elements of the periodic table are arranged as such because of several different things that help arrange them into categories. Those categories are metals, metalloids, and nonmetals. Metals are to the far left of the periodic chart, while nonmetals are found to the far right. Metalloids are at the borderline between metals and nonmetals, the zigzag line starting with boron and silicon, reaching stair-step wise down to astatine. All these elements differ by the number of electrons in their outer electron shell. Most of the metals have a few electrons, it is easier for them to donate those electrons than secure enough to fill all the vacancies in their outer electron shell. Likewise, nonmetals have a few vacancies to fill in their outer electron shell, so it is easier to fill those than give up all those electrons already there. Metalloids are the go-betweens, sharing properties of both metals and metalloids.