MCQ practice · SSC Chemistry Board questions · Chapter 3: Structure of Matter
How many electrons are in the ion ²⁷₁₃Al³⁺?
Think it through first, then pick an option.
- a 3
- b 10
- c 13
- d 27
Answer and explanation
Correct answer: b 10
Aluminium's 13 electrons minus the 3 lost leave 10 in Al³⁺.
Why the other options are wrong
- a 3: 3 is the charge, the electrons lost; 13 − 3 = 10 remain.
- c 13: 13 is the neutral atom's electron and proton count; the ion has 10 electrons.
- d 27: 27 is the mass number; electrons are 13 − 3 = 10.
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