The atomic number of nitrogen is 7. Nitrogen-15 has a greater mass number than nitrogen-14 because the atomic nucleus of nitrogen-15 contains ________.

• A. 7 neutrons.
• B. 8 neutrons.
• C. 8 protons.
• D. 15 protons.

Answer: (B)

Verified step by step guidance

1. Understand that the atomic number of an element represents the number of protons in its nucleus. For nitrogen, the atomic number is 7, which means it has 7 protons.
2. The mass number of an isotope is the sum of protons and neutrons in the nucleus. Therefore, the mass number of nitrogen-15 is 15.
3. To find the number of neutrons in nitrogen-15, subtract the number of protons (7) from the mass number (15).
4. Perform the subtraction: 15 (mass number) - 7 (protons) = 8 neutrons.
5. Conclude that nitrogen-15 has 8 neutrons in its nucleus, which is why it has a greater mass number than nitrogen-14, which has 7 neutrons.