Technetium is a radioactive silver-gray metal.
In some of its chemical properties it resembles rhenium, the element below it in group VIIb of the periodic table . It tarnishes slowly when exposed to moist air. Although it is not attacked by hydrochloric acid, it dissolves in concentrated sulfuric or nitric acid and in aqua regia. The pure metal may be prepared by chemical reduction of certain of its compounds with hydrogen gas. This use is limited by the radioactivity of the element.