They were given the name halogen from the Greek roots hal - salt and - gen to produce because they all produce sodium salts of similar properties of which sodium chloridetable salt or halite is best known. It is a pale yellow corrosive gas which reacts with most organic and inorganic substances. Oxygen On The Periodic Table Of The Elements Ad Periodic Oxygen Elements Table Ad Oxygen Periodic Table Of The Elements Periodic Table The halogen elements are fluorine F chlorine Cl bromine Br iodine I astatine At and tennessine Ts. . Compare Chlorine with other Group 17 elements. The important trends are These trends arise due to changes in the structure of atoms of the elements within their groups and periods. Fluorine like Teflon is used to make plastics and is also important in dental health. Through wind-blown soil fluorides are released into the air. Two different elements have similar chemical properties when they have the