Why the elements of 17th group are known as halogens and that of 16th group are known as chalcogens?
Group 16 elements are called chalcogens. The word chalcogen means ore forming. The name is actually derived from a Greek word. These electronegative elements are strongly associated with metal-bearing minerals, where they have formed water-insoluble compounds with the metals in the ores. Metal chalcogens are common as minerals. For example, pyrite (FeS2) is an iron ore.
Group 17 elements are called halogens. The word halogen is also derived from a Greek word meaning "to produce salt" because a salt is formed in reactions involving these elements. The group 17 elements form salts namely fluorides, chlorides, bromides and iodides.