An ion has 107 electrons, 107 protons, and 109 neutrons. What is the mass number of this ion?

• A. 216
• B. 109
• C. 214
• D. 107

Answer: (A)

Verified step by step guidance

1. Identify the definition of mass number: it is the total number of protons and neutrons in the nucleus of an atom or ion.
2. Note that the number of protons is given as 107 and the number of neutrons is given as 109.
3. Write the formula for mass number: \(\text{Mass number} = \text{Number of protons} + \text{Number of neutrons}\).
4. Substitute the given values into the formula: \(\text{Mass number} = 107 + 109\).
5. Add the numbers to find the mass number (do not calculate the final sum here, just set up the expression).