Aqueous solutions of two compounds ${\mathrm{M}}_1-\mathrm{O}-\mathrm{H}$ and ${\mathrm{M}}_2-\mathrm{O}-\mathrm{H}$are prepared in two different beakers. If, the electronegativity of ${\mathrm{M}}_1=3.4$, ${\mathrm{M}}_2=1.2$, $\mathrm{O}$ = 3.5 and $\mathrm{H}$= 2.1, then the nature of two solution will be respectively:

According to Gallis, if the electronegativity of M in a hydroxide (MOH) is greater than 1.7, the substance will have an acidic character, and if it is less than 1.7, the substance will have a basic nature.
As a result, ${\mathrm{M}}_1= \mathrm{OH}$ will have an acidic nature, while ${\mathrm{M}}_2= \mathrm{OH}$ will have a basic nature.