Give the formulas of the oxocations of the $3d$ series metals.

Identify $(A)$,$(B)$ and $(C)$ in the given reaction sequence:

Amphoteric oxide$(s)$ of $Mn$ is/are:

Generally,metal ions and their salts are coloured due to the presence of unpaired electrons in the metal ions. Which of the following compounds is coloured?

The highest oxidation state of $Mn$ is exhibited in $Mn_2O_7$. The correct statements about $Mn_2O_7$ are:
$(A)$ $Mn$ is tetrahedrally surrounded by oxygen atoms.
$(B)$ $Mn$ is octahedrally surrounded by oxygen atoms.
$(C)$ Contains $Mn-O-Mn$ bridge.
$(D)$ Contains $Mn-Mn$ bond.
Choose the correct answer from the options given below:

$Fe(OH)_2$ is precipitated from $Fe(II)$ solutions as a white solid but turns dark green and then brown due to the formation of: