the halogens are chemical elements under the second-to-right column in the periodic table, also known as group 17. the elements in the group are fluorine, chlorine, bromine, iodine, astatine, and tennessine. halogen literally means "salt becomer", but it is often said to mean "salt producer". they are very reactive, so they are likely to join with other elements on the left side of the periodic table to make compounds. this is because they are missing one electron. they are rarely found alone in nature. fluorine is the most reactive, while iodine is the least reactive. astatine is very radioactive and hard to get.