Which of the following correctly describes a neutral atom of nitrogen with a mass number of 15?

• A. 7 protons, 8 neutrons, 7 electrons
• B. 8 protons, 7 neutrons, 8 electrons
• C. 7 protons, 7 neutrons, 8 electrons
• D. 8 protons, 8 neutrons, 7 electrons

Answer: (A)

Verified step by step guidance

1. Recall that the atomic number of nitrogen (N) is 7, which means every nitrogen atom has 7 protons.
2. Understand that the mass number is the sum of protons and neutrons in the nucleus. Given the mass number is 15, use the formula: \(\text{mass number} = \text{protons} + \text{neutrons}\).
3. Calculate the number of neutrons by subtracting the number of protons from the mass number: \(\text{neutrons} = 15 - 7\).
4. Since the atom is neutral, the number of electrons equals the number of protons, so there are 7 electrons.
5. Combine these findings to identify the correct description: 7 protons, 8 neutrons, and 7 electrons.