Question

Lanthanoids are:

• A. 14 elements in the seventh period left ( atomic no. = 90 to 103 right ) that are filling 5f sublevel.
• B. 14 elements in the sixth period left ( atomic no. 58 to 71 right ) that are filling 4f sublevel
• C. 14 elements in the seventh period left ( atomic no. = 58 to 71 right ) that are filling 4f sublevel
• D. 14 elements in the sixth period left ( atomic no. 90 to 103 right ) that are filling 4f sublevel

Answer 1

The correct option is B 14 elements in the sixth period left ( atomic no. 58 to 71 right ) that are filling 4f sublevel

14 elements in the sixth period left ( atomic no. 58 to 71 right ) that are filling 4f sublevel.

The electronic configuration of the Lanthanoid series is $\left[Xe\right]5d^{0-1}6s^{2}4f^{0-14}$