A chemical element, V, with atomic number 23. Natural deposits contain two isotopes, ⁵⁰V (0.24%), which is weakly radioactive, and ⁵¹V (99.76%). Commercially important as an oxidation catalyst, vanadium also is used in the production of alloy steel and ceramics and as a colorizing agent. Studies have demonstrated the biological occurrence of vanadium, especially in marine species; in mammals, vanadium has a pronounced effect on heart muscle contraction and renal function.