An element A of group 1 shows similarity to an element B belonging to group 2. If A has maximum hydration enthalpy in group 1 then B is :

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : Boron is unable to form $$\mathrm{BF}_{6}^{3-}$$.

Reason (R) : Size of B is very small.

In the light of the above statements, choose the correct answer from the options given below :

In neutral or alkaline solution, $$\mathrm{MnO}_{4}^{-}$$ oxidises thiosulphate to :

Low oxidation state of metals in their complexes are common when ligands :