The atomic masses of two isotopes of Zinc are 64 and 66. If Zinc has 27 electrons, what is the number of protons and neutrons in each isotope? Zinc-64 : Number of protons Number of neutrons
Zinc-66 : Number of protons Number of neutrons

Zinc-64: Number of protons is 30. Number of neutrons 34.

Zinc-66: Number of protons is 30. Number of neutrons 36.

Explanation:

The atomic number of Zinc is 30, so in every Zinc atom, regardless of whether it's an isotope or not, will always have 30 protons.

The atomic number of an equivalent to the number of protons, and never changes.

The isotope number is the sum of the protons and neutrons in the nucleus.

Isotope number = atomic number + neutrons

So if we have 30 protons, and we're trying to find the number of neutrons in Zinc-64 we just subtract 30 from 64.

64 - 30 = 34

So now we know that there are 34 neutrons in Zinc-64

Same thing goes for Zinc-66.

66 - 30 = 36

There are 36 neutrons in Zinc-66.

Hope that's helpful!