There is a criterion for judging weak base cations. For metal elements, the more to the right in the periodic table, the weaker the alkalinity (1, 2 main groups are all strong bases), but if this cation is strongly hydrolyzed, it is already acidic, such as Fe3+, so the weak alkaline cations include copper ions, aluminum ions, ammonium ions, zinc ions, silver ions, ferrous ions, divalent manganese ions and so on.