Which of the following oxides is white but becomes yellow on heating?

Misch metal is an alloy of $:-$

Those elements whose two outermost orbitals are incompletely filled with electrons are known as:

Amongst the following,the lowest degree of paramagnetism per mole of the compound at $298 \ K$ will be shown by:

State whether the following statements are true or false:
$(i)$ Atomic size increases with an increase in the atomic number of elements.
$(ii)$ The electron gain enthalpy for noble gases is approximately zero.
$(iii)$ The first element of the actinoid series is $Th$ and the last element is $Lu$.
$(iv)$ The general electronic configuration of $d$-orbitals is always $(n-1)d^{1-10}ns^2$.

Lanthanoid contraction is responsible for which of the following?