Which of the following correctly describes how to calculate the number of neutrons in the nucleus of an atom?

• A. Multiply the atomic number by the mass number.
• B. Subtract the atomic number from the mass number.
• C. Divide the mass number by the atomic number.
• D. Add the atomic number to the mass number.

Answer: (B)

Verified step by step guidance

1. Understand the definitions: The atomic number (Z) represents the number of protons in the nucleus of an atom, and the mass number (A) represents the total number of protons and neutrons in the nucleus.
2. Recall that the number of neutrons (N) can be found by subtracting the number of protons from the total nucleons (protons + neutrons).
3. Write the relationship as an equation: \(N = A - Z\), where \(N\) is the number of neutrons, \(A\) is the mass number, and \(Z\) is the atomic number.
4. Recognize that multiplying, dividing, or adding the atomic number and mass number does not correctly isolate the number of neutrons, so those operations are incorrect for this purpose.
5. Therefore, to find the number of neutrons in an atom, subtract the atomic number from the mass number using the formula \(N = A - Z\).