Oxides and peroxides of group 2 metals

   Beryllium oxide, BeO, is formed by ignition of Be or its compounds in O₂. It is an insoluble white solid which adopts a wurtzite lattice. The oxides of the other group 2 metals are usually prepared by thermal decomposition of the corresponding carbonate.

    MgO, CaO, SrO and BaO crystallize with an NaCl lattice and the decrease in melting point reflects the decrease in lattice energy as the cation size increases . The high melting point of MgO makes it suitable as a refractory material.

    Refractory materials are suitable for use in furnace linings; such a material has a high melting point, low electrical conductivity and high thermal conductivity, and is chemically inert at the high operating temperatures of the furnace.  The action of water on MgO slowly converts it to Mg(OH)₂ which is sparingly soluble. Oxides of Ca, Sr and Ba react rapidly and exothermically with water, and absorb CO₂ from the atmosphere. The conversion of CaO to calcium carbide and its subsequent hydrolysis ( is industrially important although, as an organic precursor, ethyne is being superseded by ethene.

    Group 2 metal peroxides, MO₂, are known for M = Mg, Ca, Sr and Ba. Attempts to prepare BeO₂ have so far failed, and there is no experimental evidence for any beryllium peroxide compound.† As for the group 1 metal peroxides, the stability with respect to the decomposition below reaction  increases with the size of the M²⁺‏ ion. This trend arises from the difference between the lattice energies of MO and MO₂ (for a given M) which becomes smaller as r‏ increases; Δ_latticeH^o(MO,s) is always more negative than Δ_latticeH^o(MO₂,s) .

   All the peroxides are strong oxidizing agents. Magnesium peroxide (used in toothpastes) is manufactured by reacting MgCO₃ or MgO with H₂O₂. Calcium peroxide is prepared by cautious dehydration of CaO₂.8H₂O.

   The reactions of SrO and BaO with O₂ (600 K, 200 bar pressure, and 850 K, respectively) yield SrO₂ and BaO₂. Pure BaO₂ has not been isolated and the commercially available material contains BaO and Ba(OH)₂. Reactions of the peroxides with acids generate H₂O₂.

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