Concentrated nitric acid, upon long standing, turns yellow-brown due to the formation of

The arrangement of X^$$-$$ ions around A⁺ ion in solid AX is given in the figure (not drawn to scale). If the radius of X^$$-$$ is 250 pm, the radius of A⁺ is

Upon treatment with ammoniacal H₂S, the metal ion that precipitates as a sulphide is

The pair(s) of coordination complexes/ions exhibiting the same kind of isomerism is(are)