Name the periodic element,which does not show variable oxidation states.

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 $(n-1)d^{1-10}ns^2$.

$d-d$ transition occurs in . . . . . . .

The set of elements which obey the general electronic configuration $(n-1)d^{1-10}ns^2$ is

The magnetic moment of $M^{x+}$ (atomic number $= 25$) is $\sqrt{15} \ BM$. The number of unpaired electrons and the value of $x$,respectively,are

Which of the following has the maximum number of unpaired electrons?