Atom A- 6 protons, 6 electrons, 7 neutrons

Question

Atom D- 6 protons, 6 electrons, 8 neutrons
Atom X- 7 protons, 7 electrons, 8 neutrons
Atom Z- 8 protons, 8 electrons, 9 neutrons

Which two atoms are isotopes of the same element?

a. A and D
b. A and Z
c. X and D
d. X and Z

How am I supposed to figure this out?

Answer 1

An isotope has the same number of protons as the original element, but different number of neutrons.

I think the answer is A because atomA and atomD have the same number of protons and a different number of neutrons.

Answer 2

Moises is correct. The answer is a. A and D are isotopes.

Answer 3

thanks