Arsenic (As)

Arsenic ([Ar]3d¹⁰4s²4p³) (CAS 7440-38-2) a steel-gray, semi-metallic solid, is very brittle, crystalline, and poisonous. Elemental arsenic occurs in two solid modifications: the ordinary, stable, metallic-gray form and the yellow form. It oxidizes in air and, when heated, is rapidly oxidized to arsenous oxide (AS₂O₃) with a garlic odor. Arsenic is used as a doping agent in semiconductor materials.