Question

Although +3 is the characteristic oxidation state for lanthanoids,But cerium also shows +4 oxidation state because ___________.

• A. it resembles $P{b}^{4+}$.
• B. it has a tendency to attain $f^0$ configuration.
• C. it has variable ionisation enthalpy.
• D. it has a tendency to attain noble gas configuration.

Answer 1

Answer: (B), (D)

it has a tendency to attain noble gas configuration.

Atomic number of Cerium is 58

The electronic configuration of Ce
is [Xe ] $4f^{1}5d^{1}6s2$.

The characteristic oxidation state of
Lanthanoids is +3. Which was obatained by
loosing three electrons from $5d^{1}and6s^2$.

Cerium (Ce) tends to lose the outer 4
electrons and attain stable configuration $i.e.,$ [Xe]$4f^{\circ }5d^{\circ }6s^{\circ }$ which obviously is a noble gas configuration .

Thus, Ce exhibts +4 oxidation state to attain noble gas configuration and to have zero electrons in $4f-orbital.$