Editing Hydroxide (section)

===Alkaline earth metals===
[[File:Beryllium trimer.svg|thumb|left|130px|Trimeric hydrolysis product of beryllium dication<ref group=note>In aqueous solution the ligands L are water molecules, but they may be replaced by other ligands</ref>]]
[[File:BeHydrolysis.png|thumb|Beryllium hydrolysis as a function of pH. Water molecules attached to Be are omitted.]]
[[Beryllium hydroxide]] Be(OH)<sub>2</sub> is [[amphoteric]].<ref name=amph>Thomas R. Dulski [https://books.google.com/books?id=ViOMjoLKB1gC&pg=PA100 A manual for the chemical analysis of metals], ASTM International, 1996, {{ISBN|0-8031-2066-4}} p.&nbsp;100</ref> The hydroxide itself is [[insoluble]] in water, with a [[solubility product]] log&nbsp;''K''*<sub>sp</sub> of −11.7. Addition of acid gives soluble [[hydrolysis]] products, including the trimeric ion [Be<sub>3</sub>(OH)<sub>3</sub>(H<sub>2</sub>O)<sub>6</sub>]<sup>3+</sup>, which has OH groups bridging between pairs of beryllium ions making a 6-membered ring.<ref>{{cite journal|last=Alderighi|first=L|author2=Dominguez, S. |author3=Gans, P. |author4=Midollini, S. |author5=Sabatini, A. |author6= Vacca, A. |year=2009|title=Beryllium binding to adenosine 5'-phosphates in aqueous solution at 25°C|journal=J. Coord. Chem.|volume=62|issue=1|pages=14–22|doi=10.1080/00958970802474862|s2cid=93623985}}</ref> At very low pH the [[Metal ions in aqueous solution|aqua ion]] [Be(H<sub>2</sub>O)<sub>4</sub>]<sup>2+</sup> is formed. Addition of hydroxide to Be(OH)<sub>2</sub> gives the soluble tetrahydroxoberyllate or tetrahydroxido[[beryllate]] anion, [Be(OH)<sub>4</sub>]<sup>2−</sup>.

The solubility in water of the other hydroxides in this group increases with increasing [[atomic number]].<ref>Housecroft, p.&nbsp;241</ref> [[Magnesium hydroxide]] Mg(OH)<sub>2</sub> is a strong base (up to the limit of its solubility, which is very low in pure water), as are the hydroxides of the heavier alkaline earths: [[calcium hydroxide]], [[strontium hydroxide]], and [[barium hydroxide]]. A solution or suspension of calcium hydroxide is known as [[limewater]] and can be used to test for the [[weak acid]] carbon dioxide. The reaction Ca(OH)<sub>2</sub> + CO<sub>2</sub> {{eqm}} Ca<sup>2+</sup> + {{chem|HCO|3|−}} + OH<sup>−</sup> illustrates the basicity of calcium hydroxide. [[Soda lime]], which is a mixture of the strong bases NaOH and KOH with Ca(OH)<sub>2</sub>, is used as a CO<sub>2</sub> absorbent.