The number of unpaired electrons in $Cr^{+}$ will be

The number of valence electrons in $Fe^{2+}$ ion $(Fe = 26)$ is .......

Consider the following pairs of elements and identify the pairs of elements which have nearly same atomic radius.
$I$. $Y, La$
$II$. $Zr, Hf$
$III$. $Mo, W$
$IV$. $Cr, Mo$

Given below are two statements:
Statement $I :$ The $E^{\circ}$ value of $Ce^{4+} / Ce^{3+}$ is $+1.74 \, V$.
Statement $II :$ $Ce$ is more stable in $Ce^{4+}$ state than $Ce^{3+}$ state.
In the light of the above statements,choose the most appropriate answer from the options given below:

The common oxidation state of scandium $(Sc)$,a transition element,is:

Which of the following ions is diamagnetic?