Question

deuterium and tritium are isotopes of hydrogen. what is different about them?
o they have different numbers of neutrons.
o they have different numbers of protons.
o they have different atomic numbers.
o they have different numbers of electrons.

Explanation:

Isotopes of an element have the same number of protons (and thus the same atomic number) and electrons. The difference between isotopes lies in the number of neutrons. Deuterium and tritium, as isotopes of hydrogen, have different neutron - counts.

Answer:

They have different numbers of neutrons.