The difference between the radii of 3^rd and 4^th
orbits of Li²⁺ is R₁ . The difference between the
radii of 3^rd and 4^th orbits of He⁺ is $$\Delta $$R₂ .
Ratio $$\Delta $$R₁ : $$\Delta $$R₂ is :

Which of the following derivatives of alcohols is unstable in an aqueous base?

The correct electronic configuration and spin-only
magnetic moment (BM) of Gd³⁺ (Z = 64), respectively, are :

In the following reaction sequence the major products A and B are :