Question

How many neutrons are in an atom of this isotope if the atomic number of yttrium is 39 and the atomic mass of the isotope is 89?

Answer 1

The atomic number of yttrium is 39 and the mass number is 89.

The electrons contribute negligible mass to the atom.

So, Weight of atom=weight of protons + Weight of neutrons.

89=39+n, where n is the number of neutrons.

So, the number of neutrons is 50.