The electronic configuration of Curium (Atomic number $96$) is

Which of the following elements shows the maximum number of different oxidation states in its compounds?

Use Hund's rule to derive the electronic configuration of $Ce^{3+}$ ion and calculate its magnetic moment on the basis of 'spin-only' formula.

Identify the incorrect statement among the following.

In the lanthanide series,the element well known to exhibit $+4$ oxidation state is

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: $5f$ electrons can participate in bonding to a far greater extent than $4f$ electrons.
Reason $R$: $5f$ orbitals are not as buried as $4f$ orbitals.
In the light of the above statements,choose the correct answer from the options given below: