How can you tell if a metal ion will hydrolyze to form an acidic solution?
So the ability of a metal cation to hydrolyze water molecules to form acidic solutions is based on the charge of the ion and the size of the atom. The larger atoms will stabilize charge better (i.e. it spreads it out over a larger space). Unstable cations form hydroxides or oxides with water molecules and release hydronium ions.
Estimations of the acidity for metal cations can be found with the equation below,
$pka = 15.14 - 88.16(\frac{Z^2}{r})$
Z being the charge of the ion and r being the atomic radius. I bold the word estimation cause this isn’t a perfect system and I want to make that clear. However, better equations do exist.
Electronegativity does play a role too. The more electronegative a metal cation is, the more acidic it will be.
I would recommend taking a look at this link for more information