The smallest Z2/r ratios undergo the least hydrolysis and belong to cations termed nonacidic cations. Elements with electronegativities less than 1.5 and Z2/r less than 0.01 undergo negligible hydrolysis and not noticable change in pH occurs when these ions are added to water. The hydroxides of these ions do not precipate from aqueous solution. In fact, the solid hydroxides of these cations deliquesce in humid are (remove water from the air to form a solution.) Most Group IA ions fit into this category.
	Ions which have Z2/r between 0.01 and 0.04 hydrolyze enough to be measured in sensitive experiments. These cations are termed feebly acidic cations. Their hydroxides do not normally precipitate from aqueous solution. These hydroxides are less soluble than the hydroxides of nonacidic cations. Li+, Ba2+, Sr2+,and Ca2+ fit into this category.
	The acidity of cations with Z2/r ratios that range between 0.04 and 0.10 is important to the chemistry of these ions. Experimentally, this acidity is not obvious in simple experiments due to the acidity induced by the carbon dioxide dissolved in the water. Ions in this category are termed weakly acidic. Many ions in this category are biologically important such as Mg2+ and +2 ions of some transition metals. The biological functions of these ions revolve around their acidity. Ions in this category react with moderate concentration of OH- to precipitate insoluble metal hydroxides in neutral and slightly basic solutions.
	Cations with Z2/r ratios between 0.10 and 0.16 are clearly acidic. These ions are termed moderately acidic and have pKa values comparable to organic acids such as acetic acid. Often aqueous solutions of these ions will be cloudy due to the formation of some insoluble mrtal hydroxide. To keep the hydroxides dissolved, solutions of these cations should be kept highly acidic. Al3+ and +3-charged transition metals fall into this category
	Cations with Z2/r ratios between 0.16 and 0.22 react violently with water and hydrolyze almost completely. The resulting solutions are strongly acidic producing large amounts of metal hydroxide or oxide precipitate. The precipitation usually can be redissolved by adding concentrated HCl. Cations in this category are termed strongly acidic cations. Ti4+ fits into this category.
	Cations with Z2/r ratios greater than 0.22 react irreversibly with water to yield hydroxides or oxides. The greater the value of Z2/r, the greater the acidity of the metal hydroxide. These metal hydroxides ionize to form oxo anions. These cations are termed very strongly acidic cations and do not remain as cations in solution.