Question

The 71^st electron of an element X with an atomic number of 71 enters into the orbital:

• A. 4s
• B. 5s
• C. 5d
• D. 6s

Answer 1

The correct option is C

5d

The element X with atomic number 71 is lutetium and its electronic configuration is $\left[\mathrm{Xe}\right]4{\mathrm{f}}^{14}6{\mathrm{s}}^{2}5{\mathrm{d}}^1.$

The last electron will enter in 5d orbital.

Conclusion Statement: Hence, Option (C) is correct.