Select the correct statement `(s)`.

Options

A. `Cr^(2+)` compounds are ionic.
B. They are oxidised to `Cr^(3+)` by air.
C. They are reducing agent in aqueous solution.
D. None is correct.

Answer

A, B, C

Explanation

The variability of oxidation states `(OS)`, a characteristic of transition elements `(TE)` arises out of incomplete filling of `d`-orbitals in such a way that their `OS` differ from each other by unity.
`Cr` is most stable in `+3` and `6 OS`.
Lower oxidation states of `TE` forms mostly ionic compounds. `Cr (Z = 24) rArr 3d^(5)4s^(1), Cr^(2+) rArr 3d^(4)`
`Cr^(2+) rarr cr^(3+) + e^(-) [["Oxidation and thus"],["acts as reducing agent"]]`
`[[3d^(4)],["cofiguration"],["less stable"]] [[3d^(3) "configuration is more"],["stable due to half-filled orbitals" ","],[i.e. t_(2g) "level".]]`