Fluorine is the 9th element of the periodic table. It is a gas. Fluorine is added to city water to prevent tooth decay, and is also used in toothpaste to do the same. They are also used in aerosol cans and air conditioners.
Chlorine is the 17th element of the periodic table. It is a gas. Because it combines with almost every element it is never found free in nature. It is used to make drinking water safe and to take care of swimming pools. It is also used in the process of making many thinks like paper, medicines, and dyes and paints. It is also used to make table salt.
Bromine is the 35th element of the periodic table. The only nonmetal element that is liquid at room temperature. It was originally used to protect engines from leaded gasoline but is now not used because we now use unleaded gasoline. Now it is mostly used in photography paper.
Iodine is the 53rd element of the periodic table. Its first use is a test for starch. Another is to make photographic paper, and lastly there is antiseptic for wounds.
Astatine is the 85th element of the periodic table. There are no known uses of this element because there are less than 50 grams in the world. So it is primarily for research.
