The halogens

The halogens are a group of five elements of the periodic table. They are Fluorine, Chlorine, Bromine, Iodine, and Astatine. They all have seven outer electrons except for astatine. Their compounds and ions are called halides. Let's take a look at these elements.

This one is Fluorine. Alone it is F2.It is the most reactive of the halogens and it reacts with almost all the elements. Its atomic number is 9 and its atomic weight is 18.99. It is a pale yellow-green gas and is very poisonous. It is never used in school laboratories because it attacks glass, but it can be useful in substances like toothpaste. It is found in xenon tetrafluoride (XeF4), freon (CF2Cl2), fluorospar (CaF2), and cryolite (Na3AlF6)as well as many other compounds.

  After fluorine is chlorine. Chlorine's atomic number is 17 and its atomic weight is 35.45. In the picture it is shown on its own but it only occurs naturally in compounds. As with fluorine it is a gas but it is greener. Its most well-known compound is salt (NaCl). It is also found in sodium hypochlorite (NaOCl)which is used to make paper white. Hydrogen chloride (HCl) is a colorless gas that is made by burning hydrogen in chlorine. It dissolves in water to form hydrochloric acid which is used to etch metals.

Next is bromine. It is one of the two liquids on the periodic table (mercury is the other) and it gives off toxic fumes. Its atomic number is 35 and its atomic weight is 79.91. Alone it is Br2 but, like chlorine it is only naturally found in compounds. Its most common compound is sodium bromide (NaBr) which is found in sea water. Another compound, silver bromide (AgBr)is used in photography, while yet another compound, hydrogen bromide has the same properties of hydrochloric acid.

This one is Iodine. Its atomic number is 53 and its atomic weight is 126.90. It is found in foods such as seaweed, seafood, cod liver oil, and fruits and vegetables. Don't panic about that because it it healthy. When heated it gives off a purple vapor. Like the other halogens it is paired up with sodium, this time in sodium iodate (NaIO3). Iodine dissolved in ethanol (C2H5OH) is called tincture of iodine and is dabbed on cuts.

There is not much to say about astatine besides it is a radioactive, unstable element.