$$C{e^{ + 3}},\,\,L{a^{ + 3}},\,\,P{m^{ + 3}}\,\,$$ and $$Y{b^{ + 3}}\,\,$$ have ionic radial in the increasing order as

Picric acid is :

The type isomerism present in nitropentammine chromium $$\left( {{\rm I}{\rm I}{\rm I}} \right)$$ chloride is :