Question

Element A has 15 protons. Determine the number of neutrons in its isotope with mass number 33.

Answer 1

Isotope of element A has a similar number of protons but different number of neutrons and atomic mass.
33-15= 18 neutrons

Answer 2

Mass number - protons = neutrons

33 - 15 = 18

The number of neutrons here would be: 18