Q.RbO₂ is

The common compounds of the alkali metals are, as a family, predominantly ionic.

Oxides/hydroxides: combustion in excess air gives normal oxides M₂O, which react with water to give the hydroxide (M₂O + H₂O → 2MOH). Every metal except Li also forms a peroxide (M₂O₂ + 2H₂O → 2MOH + H₂O₂, M = Na,K,Rb,Cs); every metal except Li and Na also forms a superoxide (2MO₂ + 2H₂O → 2MOH + H₂O₂ + O₂, M = K,Rb,Cs). Oxides/peroxides are colourless, superoxides yellow/orange; peroxides are diamagnetic, superoxides paramagnetic (unpaired electron); Na₂O₂ is a widely used oxidising agent. The hydroxides are white, strongly basic crystalline solids that dissolve in water with evolution of heat.

Halides: colourless, high-melting MX crystals (X = F,Cl,Br,I), made from the oxide/hydroxide/carbonate + aqueous HX. Ionic except LiBr and LiI (covalent character); all water-soluble except LiF (high lattice enthalpy, both ions small) -- LiBr/LiI are additionally soluble in organic solvents. …