The Greedy Non-Metals

If alkali metals are desperate to GIVE away electrons, halogens are desperate to TAKE them. Fluorine is so aggressive it will react with almost anything — even glass! Chlorine was used as a weapon in World War I because it's so reactive and toxic. Yet these dangerous elements are essential: chlorine keeps our swimming pools clean and our drinking water safe; iodine is added to salt to prevent thyroid problems; and every time you add table salt to your food, you're eating a compound made from the explosive metal sodium and the poisonous gas chlorine. Chemistry is full of surprises!