Which pair has the same principal quantum number value for last electron?
Correct answer: B. CI & Ar
- A. H & Li
- B. CI & Ar
- C. K & Rb
- D. Na & Ne
Explanation
Principal quantum number can be determined by looking at the period number. Two elements in the same period will have the same quantum number. The principal quantum number of Cl is 3 while for Ar, it is also 3. Hence, option B is correct.
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