Individual atoms are made up of the nucleus at the center, and a series of shells around them. These shells contain a certain amount of electrons. The first shell can only hold two, as the electrons, both being charged negatively, repel each other. The second shell can hold eight, the third can contain eighteen, and so on. Now, one very interesting thing is that atoms love the number eight. So much so, that every element is trying as hard as possible to have only eight electrons in their outermost shell. Now, before I go on, let’s think about salt. As you know, salt is made up of Sodium Chloride. “Wait” you say, “isn’t Sodium one of the Alkali metals? Isn’t it going to explode in my stomach if I eat it?” Well, yes, you are right. And if you inhale a whiff of pure Chlorine gas, one moment you will be writhing on the ground in pain, and the next, dead. Yup, that’s what we season our food with.So here is why we are not dead: Remember in my last post, I said that the Alkali metals have an extra electron far out from the Nucleus, the only electron in that shell. The shell just inside it, however, has exactly eight. And way on the other side of the periodic table, we have the Halogens, which include Chlorine. These Elements each have exactly seven electrons in their outermost shell. So, we have Sodium, an Alkali, trying to get rid of an electron, and we have Chlorine, a Halogen, trying to gain an Electron. When combined, Chlorine sees Sodium’s electron, and grabs it, Sodium lets him have it. The force with which Chlorine grabs it however, is a little explosive, as, you remember, that little electron has a lot of energy. The smoke that comes forth, however, is common table salt.One more thing, you remember the Noble gases? Well, the reason they are so Noble is because they already have eight electrons in their outermost shell, so they are not readily giving away nor trying to grab an electron, making them very stable.