Chromium is a lustrous, brittle, hard metal. Its color is silver-gray and it can be highly polished. It does not tarnish in air, when heated it borns and forms the green chromic oxide. Chromium is unstable in oxygen, it immediately produces a thin oxide layer that is impermeable to oxygen and protects the metal below.
(Cr Atomic Number: 24. Atomic Mass: 51.9961 amu. Melting Point: 1857.0 °C (2130.15 K, 3374.6 °F) Boiling Point: 2672.0 )