Which of the following represents a pair of isotopes?

• A. 23Na and 24Mg
• B. 12C and 14C
• C. 16O and 16N
• D. 1H and 2He

Answer: (B)

Verified step by step guidance

1. Recall that isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.
2. Identify the atomic number (number of protons) for each element in the pairs given. For example, carbon (C) has 6 protons, sodium (Na) has 11 protons, magnesium (Mg) has 12 protons, oxygen (O) has 8 protons, nitrogen (N) has 7 protons, hydrogen (H) has 1 proton, and helium (He) has 2 protons.
3. Compare the pairs to see if they have the same atomic number but different mass numbers (sum of protons and neutrons). For instance, 12C and 14C both have 6 protons but different mass numbers (12 and 14 respectively), indicating they are isotopes.
4. Check the other pairs to confirm they do not have the same number of protons, so they are not isotopes but different elements or ions.
5. Conclude that the pair with the same atomic number but different mass numbers represents isotopes, which in this case is 12C and 14C.