How many neutrons down lanthanum-141 have in its nucleus?

Answer 1

Lanthanum's atomic number is 57 thus it has 57 protons, the number of protons an atom has is equal to the atomic weight, in this case 141 minus the number of protons or 57 so,

141-57=84

Lanthanum-141 has 84 neutrons.

Answer 2

Lanthanum-141, which has an atomic number of 57, has 84 neutrons in its nucleus. This can be calculated by subtracting the atomic number from the mass number.