Question

Is Iridium a metal or a nonmetal?

Answer 1

Iridium, `Z=77`, is a transition metal.

Explanation:

Iridium is horrendously dense (`rho>23*g*cm^-3`), and also horrendously expensive. When you work with iridium (often its salts are loaned out to researchers), you are very careful to collect all the residues so that they can be returned to the source.