What element with a mass number of 100 has 56 neutrons in its nucleus?

Barium - Ba

Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.

Symbol: Ba

Atomic mass: 137.327 u

Electron configuration: [Xe] 6s2

Atomic number: 56

Van der Waals radius: 268 pm

Discoverers: Humphry Davy, Carl Wilhelm Scheele