Number of electrons present in $4f$ orbital of $Ho^{3+}$ ion is $.....$
(Given Atomic No. of $Ho=67$)

Assertion $(A)$: Transition elements have higher enthalpies of atomization.
Reason $(R)$: Large number of unpaired electrons present in transition elements facilitate strong interatomic interaction and strong bonding between atoms.

Out of $Cu_2Cl_2$ and $CuCl_2$,which is more stable and why?

The metal ion which does not form coloured compounds is

Which element from the following in $+2$ oxidation state exhibits the highest magnetic moment?

In the $3d$ transition series,as the atomic number increases,the paramagnetic character: