How many neutrons are present in an atom of the isotope Hg-201?

• A. 201
• B. 201
• C. 80
• D. 121

Answer: (D)

Verified step by step guidance

1. Identify the atomic number (Z) of mercury (Hg), which is the number of protons in the atom. For Hg, Z = 80.
2. Recognize that the isotope notation Hg-201 means the mass number (A) is 201. The mass number is the total number of protons and neutrons in the nucleus.
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: \(N = 201 - 80\), which gives the number of neutrons in the Hg-201 isotope.