An atom has 11 protons and 12 neutrons. What is its mass number?
Answer and explanation
Correct answer: D. 23
- Step 1: Mass number = protons + neutrons = 11 + 12 = 23. Answer: 23. Why not the others: 11: That is the number of protons, the atomic number. 12: That is the number of neutrons only. 1: That is the difference between neutrons and protons.
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