Question

The atomic and mass numbers for four different atoms are given below. Which two are isotopes?

Select one:
a. W and X
b. X and Y
c. W and Y
d. Y and Z

Answer 1

@aaronq

Answer 2

Isotopes are atoms with the same number of protons but different number of neutrons.

For example, Carbon-13 and Carbon-14. Both have 6 protons but they differ in the number of neutrons.

C-13 has 7 neutrons and C-14 has 8 neutrons. Hence the protons and neutrons added together give you the mass number.