A pink colored salt on dry heating becomes blue in colour. Salt may contain 

Cuprous ion is colourless, while cupric ion is coloured because

The element the usually does $NOT$ show variable oxidation states is

Technetium, the element below manganese in the Periodic Table, would be expected to have high values for its 
$(I)$ melting point $(II)$ boiling point $(III)$ density

Which of the following statements are correct about $Zn,\,Cd$ and $Hg$ ?

$(I)$ they exhibit high enthalpies of atomisation as the $d-$ subshell is full

$(II)$ $zn$ and $Cd$ do not show variable oxidation states while $Hg$ shows $+ I$ and $+ II$

$(III)$ Compound of $Zn,\,Cd$ and $Hg$, are paramagnetic in nature

$(IV)$ $Zn,\,Cd$ and $Hg$ are called soft metals

Among $\mathrm{VO}_2^{+}, \mathrm{MnO}_4^{-}$and $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$, the spin-only magnetic moment value of the species with least oxidising ability is...................$BM$ (Nearest integer).

(Given atomic member $\mathrm{V}=23, \mathrm{Mn}=25, \mathrm{Cr}=24$ )