The ability of transition metal ions to form complex compounds is due to:

Assertion : Cuprous ion $(Cu^+)$ has unpaired electrons while cupric ion $(Cu^{2+})$ does not.
Reason : Cuprous ion $(Cu^+)$ is colourless whereas cupric ion $(Cu^{2+})$ is blue in the aqueous solution.

Why do $CrO_3$ and $V_2O_5$ have low melting points?

The pair that has similar atomic radii is

In the first transition series,the metallic bond strength increases from ..... to .....

Which of the following ions gives a coloured solution?