Which nuclide has equal numbers of protons, neutrons and electrons?

Which nuclide has equal numbers of protons, neutrons and electrons?

• A. 9B (Z = 5)
• B. 14N (Z = 7)
• C. 13C (Z = 6)
• D. 17O (Z = 8)

Answer: (B)

In a neutral atom, the number of electrons equals the number of protons. For all three counts to be the same, the neutrons must equal the protons as well, so N = Z. Since the mass number A = Z + N, having N = Z gives A = 2Z. Check the nitrogen isotope with mass number 14: Z is 7, so N = A − Z = 14 − 7 = 7. This yields 7 protons, 7 neutrons, and 7 electrons, all equal. The other options have N not equal to Z, so their counts don’t match. Therefore, 14N is the nuclide with equal numbers of protons, neutrons, and electrons.

In a neutral atom, the number of electrons equals the number of protons. For all three counts to be the same, the neutrons must equal the protons as well, so N = Z. Since the mass number A = Z + N, having N = Z gives A = 2Z. Check the nitrogen isotope with mass number 14: Z is 7, so N = A − Z = 14 − 7 = 7. This yields 7 protons, 7 neutrons, and 7 electrons, all equal. The other options have N not equal to Z, so their counts don’t match. Therefore, 14N is the nuclide with equal numbers of protons, neutrons, and electrons.