How many neutrons are present in an atom of lead (Pb) with a mass number of 208?

• A. 82
• B. 48
• C. 208
• D. 126

Answer: (D)

Verified step by step guidance

1. Identify the atomic number (Z) of lead (Pb), which is the number of protons in the nucleus. For lead, Z = 82.
2. Note the mass number (A) given in the problem, which is the total number of protons and neutrons in the nucleus. Here, A = 208.
3. Recall 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 the number of neutrons: \(N = A - Z\).
5. Substitute the known values into the equation: \(N = 208 - 82\), which will give the number of neutrons in the lead atom.