Transition elements with lower oxidation states act as........

Assertion $(A)$: $CuI_2$ cannot be prepared by the reaction of $Cu^{2+}_{(aq)}$ with $I^{-}_{(aq)}$.
Reason $(R)$: Aqueous $Cu^{2+}$ solution is blue in colour.
The correct answer is:

How are transition metals and their oxides used in industrial processes?

Identify the incorrect statement.

What is the general molecular formula of the products obtained on heating lanthanoids $(Ln)$ with sulphur?

Among $K, Ca, Fe,$ and $Zn$,the element which can form more than one binary compound with chlorine is