Question
Mass numbers of 3 atoms are 31, 32 and 34, having numbers of neutron 16, 17 and 18 respectively. Which two of them are isotopes and why?
Answer
The two atoms with mass numbers 32 and 34 are isotopes because they have the same number of protons (since they are both of the same element) but different numbers of neutrons (17 and 18, respectively). The atom with mass number 31 is a different element since it has one fewer protons.
