MCQ practice · SSC Chemistry Board questions · Chapter 3: Structure of Matter
When forming an ion, potassium gains the electronic configuration of which element?
Think it through first, then pick an option.
- a Ar
- b Cr
- c Kr
- d Sr
Answer and explanation
Correct answer: a Ar
K (2, 8, 8, 1) loses one electron to become K⁺ with 18 electrons (2, 8, 8), like argon.
Why the other options are wrong
- b Cr: Chromium has 24 electrons; K⁺ has 18, the same as argon (2, 8, 8).
- c Kr: Krypton is a much larger element; K⁺'s 18 electrons match argon.
- d Sr: Strontium is not in this chapter's table; K⁺'s 18 electrons are like argon's.
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