what determines solubility of Group 1 halides & oxides??
All common compounds of group 1 - alkali metals are soluble.
Oxides of group 1 elements readily hydrolyze to give the corresponding hydroxides. Similarly halides of group 1 elements are also soluble in water.
Solubility of metal oxides and metal halides is determined usually by lattice enthalpies and hydration enthalpies of the compounds. Higher lattice enthalpy leads to low solubility and higher hydration enthalpies lead to increased solubility.