where are the heavy metals located on the periodic table
Heavy metals Criteria based on chemical behaviour or periodic table position have been used or suggested. The United States Pharmacopeia includes a test for heavy metals that involves precipitating metallic impurities as their coloured sulfides."[6][n 3] In 1997, Stephen Hawkes, a chemistry professor writing in the context of fifty years' experience with the term, said it applied to "metals with insoluble sulfides and hydroxides, whose salts produce colored solutions in water and whose complexes are usually colored". On the basis of the metals he had seen referred to as heavy metals, he suggested it would useful to define them as (in general) all the metals in periodic table columns 3 to 16 that are in row 4 or greater, in other words, the transition metals and post-transition metals.[9][n 4] The lanthanides satisfy Hawkes' three-part description; the status of the actinides is not completely settled.[n 5][n 6]