Acid-Base Behaviour of Oxides & Hydroxides :
The oxide or hydroxide of an element may act either a base or an acid depending upon its ionization energy. If the ionization energy is low, it acts as a base and if the ionization energy is high, it acts as an acid. The ionization energies of alkali metals are the lowest, therefore, their oxides and hydroxides are the `text(strongest bases.)` Further, since the ionization energies of alkali metals decrease down the group, the basic character of their hydroxides increases in the same order : `CsOH > RbOH> KOH> NaOH> LiOH`.
The ionization energies of halogens are quite high, therefore, their oxides are the strongest acids. Further, since the ionization energies decrease down the group, therefore, the acidic character of their oxides and hydroxides decreases in the same order : `HClO_4 > HBrO_4 > HIO_4`.
As we move from left to right within a period, the ionization energies usually increase and hence their oxides and hydroxides show a `text(gradual variation from strongly basic through amphoteric to strongly acidic character)`. For example, See Table.
Hence, `Cs_2O > Rb_2O > K_2O > Na_2O > Li_2O` Basic nature (Down the group)
`Ba(OH)_2 > Sr (OH)_2 > Ca(OH)_2 > Mg(OH)_2` Basic nature of hydroxide.
The ionization energies of halogens are quite high, therefore, their oxides are the strongest acids. Further, since the ionization energies decrease down the group, therefore, the acidic character of their oxides and hydroxides decreases in the same order : `HClO_4 > HBrO_4 > HIO_4`.
As we move from left to right within a period, the ionization energies usually increase and hence their oxides and hydroxides show a `text(gradual variation from strongly basic through amphoteric to strongly acidic character)`. For example, See Table.
Hence, `Cs_2O > Rb_2O > K_2O > Na_2O > Li_2O` Basic nature (Down the group)
`Ba(OH)_2 > Sr (OH)_2 > Ca(OH)_2 > Mg(OH)_2` Basic nature of hydroxide.