Chromium (Cr) is a transition metal of atomic number 24. It had an atomic weight of 51.996 and it's a transition metal. It is a silvery metallic metal that had 4 stable isotopes: Cr 50, 52, 53 and 54. Cr 51 had a half life of 27.7 days, while other isotopes and isomers ranging from Cr 42 to Cr 67 are short-lived, with a half-life of less then 24 hours.