Answer:
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
The element with a mass number in its nucleus is Ruthenium (Ru).
Let x represent the protons
Mass number=100
Neutrons =56
Hence:
100 = x +56
x=100-56
x=44
Now using periodic table of element the element with a mass number in its nucleus that has 44 protons is Ruthenium (Ru).
Inconclusion The element with a mass number in its nucleus is Ruthenium (Ru).
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