The colour and magnetic nature of manganate ion $MnO_4^{2-}$ is-

Which diagram correctly represents the change in the color of an aqueous solution of chromate ions?

Fill in the blanks:
$(1)$ Since $V_2O_5$ acts as both an acid and a base,it is an ...... oxide.
$(2)$ The $Cr$ oxide which is basic is ......,and the $Cr$ oxide which is amphoteric is ...... .
$(3)$ The formula of chromite ore is .......... .
$(4)$ The formula of sodium dichromate crystal is .......... .

$CrO_3$ is a/an ...

What are interstitial compounds? Give their examples and characteristics.

In $Cr_2O_7^{2-}$,every $Cr$ is linked to