a common nonmetallic element belonging to the halogens; best known as a heavy yellow irritating toxic gas; used to purify water and as a bleaching agent and disinfectant; occurs naturally only as a salt (as in sea water)

• 常见的非金属元素，属于卤素，一种重的黄色刺激性有毒气体，用于净化水和作漂白剂和消毒剂，仅作为盐（在海水中）天然存在