Question

`La^(+3)` ion gives a colourless compound due to
A. completely filled 4f subshell
B. empty 4f subshell
C. half filled 4f subshell
D. unpaired electron

Answer 1

Correct Answer - B
`La (57) to [Xe] 4f^0 5d^1 6s^2 to La^(3+) to [Xe] 4f^0 5d^0 6s^0`
No `e^-` in 4f orbitals .
`therefore` colourless