The valence electron shell structure of the Be atom is 2s2, its atomic radius is 89pm, the ionic radius of Be2+ is 31pm, and the electronegativity of Be is 1.57. Due to the particularly small atomic radius and ionic radius of beryllium and the relatively high electronegativity, the tendency of beryllium to form covalent bonds is more significant, unlike other elements in the same group that mainly form ionic compounds. Therefore, beryllium often exhibits anomalous properties that are different from other elements of the same family.
(1) Beryllium is easy to form a dense protective film on the surface and does not interact with water, while other metals of the same family magnesium, calcium, strontium and barium are easy to react with water.
(2) Beryllium hydroxide is amphoterical, while the hydroxides of other elements of the same family are moderately strong alkaline or strongly alkaline.
(3) Beryllium salts are strongly hydrolyzed to form tetrahedral ions [Be(H2O)4]2+, and the Be-O bond is very strong, which weakens the O-H bond, so the hydrated beryllium ions have a tendency to lose protons:
Hence beryllium salts are acidic in pure water. The salts of other elements of the same family (except magnesium) have no hydrolysis.