How many neutrons are in an atom of Al-27 (atomic number 13)?
Answer and explanation
Correct answer: D. 14
- Step 1: Neutrons = mass number − atomic number. Step 2. 27 − 13 = 14. Answer: 14. Why not the others: 27 is what you get if you give the mass number. 13 is what you get if you give the proton number. 40 is what you get if you add the proton and mass numbers.
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