Why does this formula work? My teacher gave us a formula for determining if a M-O-H like compound will act like a base or not.without explaining much.
Base if:$$|\chi_o-\chi_M|\gt|\chi_o-\chi_H|$$
Flipped inequality if acid.
I am not unable to understand why the formula works.I think its because if the diffrence in electronegativity between Oxygen and element m is high.
It is  more likely for M-O-H to break into M and O-H
.Not certain about that either.
The bond with greater electronegativity difference has greater tendency to break with help of polar $\ce{H2O}$ molecules to hydrated ions, unless it is ionic already. Electrons then stay at the oxygen as the most electronegative atom from all the three.
So if $\ce{M}$ is less electronegative then $\ce{H}$, there will be'
$$\ce{M^{(+)}-O^{(-)}-H(aq) &lt;=&gt; M+(aq) + OH-(aq)}$$
but if $\ce{M}$ is more electronegative than $\ce{H}$ , then there will be:
$$\ce{M-O^{(-)}-H^{(+)}(aq) + H2O &lt;=&gt; MO-(aq) + H3O+(aq)}$$
( The charge in parenthesis is a partial charge.)