Question

Although +3 is the characteristic oxidation state for lanthanoids but cerium also shows +4 oxidation state because ___

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

Answer 1

Answer: (B), (C)

The correct options are
B It has a tendency to attain a noble gas configuration
C It has a tendency to attain $f^0$ configuration

There is no simple explanation for this because thermodynamics (as per reduction potentials) suggests that +3 is the more stable one! In its attempt to become $Ce$, it has a tendency to attain the noble gas configuration. This may further be supported by the stability of the $f^0$ configuration.