The general valence shell electronic configuration of lanthanoides is represented by

Options

A. `(n-2)f^(1-14)(n-1)d^(0-1)ns^(2)`
B. `(n-2)f^(1-14)(n-1)d^(10)ns^(2)`
C. `(n-2)f^(0-14)(n-1)d^(0-2)ns^(2)`
D. `(n-2)f^(1-14)(n-2)d^(0-5)ns^(2)`

Answer

A

Explanation

Lanthanum, the element preceding the lanthanides in the periodic table, has the electronic configuration `[Xe] 5d^(1)6s^(2)`. Like lanthanum, the lanthanides also exhibit the stable oxidation state of `+3`. It is expected that in these elements the successive electrons will be filled in the 4f subshell, thereby the elements may have the electronic configuration form `[Xe]4f^(1) 5d^(1)6s^(2)` to `[Xe] 4f^(14) 5d^(1) 6s^(2)`. However, the actual ground state electronic configuration of lanthanides (determined by atomic spectroscopy) shows that there is an electron in 5d subshell only in Ce, Gd and Lu while in all other elements this electron is shifted to the 4f subshell. This type of shuttling of electrons can be understood in terms of the comparable energies of the 4f and 5d subshells. Whether there is an electron in 5d orbital or not, is of little importance because the lanthanides mostly form configuration of `M^(3+)` ions varies in a regular manner form `[Xe] 4f^(1)` for `Ce^(3+)` to `[Xe] 4f^(14)` for `Lu^(3+)` .