An ion has 104 electrons, 157 neutrons, and 102 protons. What is the mass number of this ion?

• A. 256
• B. 206
• C. 259
• D. 204

Answer: (C)

Verified step by step guidance

1. Identify the definition of mass number, which is the total number of protons and neutrons in the nucleus of an atom or ion.
2. Recall that the mass number (A) is calculated using the formula: \(A = Z + N\), where \(Z\) is the number of protons and \(N\) is the number of neutrons.
3. From the problem, note the given values: number of protons \(Z = 102\) and number of neutrons \(N = 157\).
4. Substitute the values into the formula: \(A = 102 + 157\).
5. Add the numbers to find the mass number, which represents the total nucleons in the ion.