Question

In most of the lanthanides, the penultimate shell contains _______ electrons in _____ orbitals.

• A. 8
• B. s and p

Answer 1

Filling of valence electrons in f-block:

The general electronic configuration of f block elements :

$(\mathrm{n}-2){\mathrm{f}}^{0-14}(\mathrm{n}-1){\mathrm{d}}^{0-1}{\mathrm{ns}}^2$

Elements in which the last electron enters any one of the seven f orbitals of their respective anti-penultimate shell are called p block elements. There are two series of f block elements each containing 14 elements. The series is placed at the bottom of the periodic table. In these elements the s orbital of the last shell is completely filled, the d orbital of the penultimate (n-1) shell contains 0 to one electron but the f orbital of the anti-penultimate (n-2) shell gets progressively filled in.

In most lanthanides, the penultimate shell contains 8 electrons in s and p orbitals.