The element that was once known as columbium is now also known as niobium and its chemical symbol is Nb. The reason for the name change was the fact that the same metal was discovered twice (the first time in 1801, a second time in 1846) but people were not aware of it and eventually niobium received the name given to it by a German chemist in 1846. The name columbium is still used in the US, but the chemical symbol Nb was generally adopted. Another interesting fact about the history of this element is that for a long time in its history it was confused with tantalum (Ta).

Niobium is a transition metal that is strong, light grey, crystalline, and ductile. Its atomic number is 41. It is used in a variety of applications, the main one being alloying of steels.

More Info: en.wikipedia.org