what is the name of the 4th halogen
Period 4 element Bromine (Br) is an element in period 4, between selenium and krypton. Bromine is a halogen, never existing in pure form in nature. Bromine is barely liquid at room temperature, boiling at about 330 kelvins. Bromine is also quite toxic and corrosive, but bromide ions, which are relatively inert, can be found in halite, or table salt. Bromine is often used as a fire retardant because many compounds can be made to release free bromine atoms.