Which nuclide has equal numbers of protons, neutrons and electrons among the following options?

Which nuclide has equal numbers of protons, neutrons and electrons among the following options?

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

Answer: (C)

In a neutral atom, the number of electrons equals the number of protons, which is the atomic number. The number of neutrons is the mass number minus the atomic number. To have equal numbers of protons, neutrons, and electrons, the neutron count must match the proton/electron count. For nitrogen-14, the atomic number is 7, so there are 7 protons and 7 electrons. The mass number is 14, so neutrons = 14 − 7 = 7. All three numbers are 7. The other options don’t fit: carbon-13 has 6 protons but 7 neutrons; oxygen-17 has 8 protons and 9 neutrons; boron-9 has 5 protons and 4 neutrons.

In a neutral atom, the number of electrons equals the number of protons, which is the atomic number. The number of neutrons is the mass number minus the atomic number. To have equal numbers of protons, neutrons, and electrons, the neutron count must match the proton/electron count.

For nitrogen-14, the atomic number is 7, so there are 7 protons and 7 electrons. The mass number is 14, so neutrons = 14 − 7 = 7. All three numbers are 7.

The other options don’t fit: carbon-13 has 6 protons but 7 neutrons; oxygen-17 has 8 protons and 9 neutrons; boron-9 has 5 protons and 4 neutrons.