Zinc has the chemical symbol Zn and the atomic number 30. How many protons, neutrons, and electrons does an atom of zinc-69 have?

A. 30 protons, 39, neutrons, 39 neutrons

B. 39 protons, 30 neutrons, 30 neutrons

C. 39 protons, 30 neutrons, 39 electrons

D. 30 protons, 39, neutrons, 30 electrons

D. 30 protons, 39 neutrons, 30 electrons

Explanation:

The atomic number (Z) is the number of protons (p) in the nucleus. Since

Z = 30, p = 30.

In a neutral atom, the number of electrons (e) equals the number of protons. Since p = 30, e = 30.

The mass number (A) is the number of protons plus the number of neutrons (n).

A = p + n

For an atom of zinc-69,

69 = 30 + n Subtract 30 from each side and transpose

n = 39

D, because isotopes all have the same atomic number but different number of neutrons