Ionic compounds are usually crystalline solids with a high melting point.
They are usually soluble in water and other highly polar solvents and not soluble in non polar solvents. Binary ionic compounds are often more stable than the elements from which they are formed, because their formation is likely to be exothermic or very exothermic. Energy is released when electrons are added to atoms of the non metal and, more importantly, when the ions come together to form the crystal lattice. The energy that is released if far greater than the amount of energy that is used.