How many neutrons are present in an atom of tin-120 (Sn-120)?

• A. 120
• B. 70
• C. 60
• D. 50

Answer: (B)

Verified step by step guidance

1. Identify the atomic number (Z) of tin (Sn) from the periodic table. The atomic number represents the number of protons in the nucleus of the atom.
2. Note that the number 120 in tin-120 (Sn-120) is the mass number (A), which is the total number of protons and neutrons in the nucleus.
3. Use the formula to find the number of neutrons (N): \(N = A - Z\), where \(A\) is the mass number and \(Z\) is the atomic number.
4. Substitute the values for tin-120: \(N = 120 - Z\) (where \(Z\) is the atomic number of tin).
5. Calculate the difference to find the number of neutrons in the tin-120 atom.