MCQ practice · SSC Chemistry Board questions · Chapter 3: Structure of Matter
Which element follows the (n − 1)d¹⁰ ns¹ configuration?
Think it through first, then pick an option.
- a Cr
- b Zn
- c Cu
- d Fe
Answer and explanation
Correct answer: c Cu
Cu is 3d¹⁰ 4s¹, that is (n − 1)d¹⁰ ns¹.
Why the other options are wrong
- a Cr: Cr follows (n − 1)d⁵ ns¹, not d¹⁰; the d¹⁰ s¹ one is Cu.
- b Zn: Zn is 3d¹⁰ 4s², with ns², not ns¹; the d¹⁰ s¹ one is Cu.
- d Fe: Fe is 3d⁶ 4s², a normal configuration; the d¹⁰ s¹ one is Cu.
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