How many neutrons are present in the nucleus of an isotope of phosphorus with a mass number of 32?

• A. 32
• B. 47
• C. 17
• D. 15

Answer: (D)

Verified step by step guidance

1. Identify the atomic number (Z) of phosphorus, which is the number of protons. For phosphorus, Z = 15.
2. Understand that the mass number (A) is the total number of protons and neutrons in the nucleus. Here, A = 32.
3. Use the relationship between mass number, protons, and neutrons: \(A = Z + N\), where \(N\) is the number of neutrons.
4. Rearrange the formula to solve for neutrons: \(N = A - Z\).
5. Substitute the known values: \(N = 32 - 15\), which gives the number of neutrons in the isotope.