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)

Among P, Q, R and S, the aromatic compound(s) is(are)