CHEMICAL PROPERTIES OF GROUP 2 ELEMENTS +𝑶𝟐 Magnesium, Mg Calcium, Ca Strontium, Sr Barium, Ba 2𝑀(𝑠) + 𝑂2 (𝑔) → 2𝑀𝑂(𝑠) Beryllium, Be +𝑶𝟐 flame colour White Brilliant white Brick red Crimson red +air 3𝑀(𝑠) + 𝑁2 → 𝑀3 𝑁2 (𝑠) Element Notes Beryllium has a very thin but strong oxide layer on its surface that prevents further oxidation. Thus, beryllium does not burn spontaneously in oxygen and air unless in powder form and heated above 1000°C. Magnesium can reduce and burn in carbon dioxide: 2𝑀𝑔(𝑠) + 𝐶𝑂2 (𝑔) → 2𝑀𝑔𝑂(𝑠) + 𝐶(𝑠) This means that magnesium fires cannot be extinguished using carbon dioxide fire extinguishers. Strontium and Barium can form peroxides when heated in excess 𝑶𝟐 : 𝑀(𝑠) + 𝑂2 (𝑔) → 𝑀𝑂2 (𝑠) Apple green The peroxides decompose to their oxides and their stabilities increases down the group. Element +𝑯𝟐 𝑶(𝒈) or +𝑯𝟐 𝑶(𝒍) +cold 𝑯𝟐 𝑶 +hot 𝑯𝟐 𝑶 Beryllium, Be 𝑀(𝑠) + 𝐻2 𝑂(𝑔) → 𝑀𝑂(𝑠) + 𝐻2 (𝑔) Magnesium, Mg Very slowly with boiling water. If a metal reacts with steam, the metal hydroxides will thermally decompose to give the oxide and water: 𝑀(𝑠) + 2𝐻2 𝑂(𝑙) → 𝑀(𝑂𝐻)2 (𝑎𝑞) + 𝐻2 (𝑔) 𝑀(𝑂𝐻)2 (𝑠) → 𝑀𝑂(𝑠) + 𝐻2 𝑂(𝑙) 𝑀(𝑠) + 𝐻2 𝑂(𝑔) → 𝑀𝑂(𝑠) + 𝐻2 (𝑔) Calcium, Ca Strontium, Sr Barium, Ba Very slow at very high temperature, above 700°C800°C. Rapid and vigorous when heated. Reacts with excess steam to form magnesium oxide and hydrogen gas: 𝑀𝑔(𝑠) + 2𝐻2 𝑂(𝑔) → 𝑀𝑔(𝑂𝐻)2 (𝑎𝑞) + 𝐻2 (𝑔) Slow 𝑀(𝑠) + 2𝐻2 𝑂(𝑙) → 𝑀(𝑂𝐻)2 (𝑎𝑞) + 𝐻2 (𝑔) +𝑯𝟐 𝑶(𝒈) Vigorous Fast Unlike the oxides formed by the other group 2 elements (alkaline earth metals), beryllium oxide is amphoteric rather than basic. Beryllium dissolves readily in non-oxidizing acids, such as HCl and diluted H2SO4, but not in nitric acid or water as this forms the oxide. This behaviour is similar to that of aluminium metal. Beryllium also dissolves in alkali solutions. Group 2 Element Group 2 Oxides Beryllium, Be BeO Magnesium, Mg Calcium, Ca Strontium, Sr Barium, Ba MgO CaO SrO BaO Physical Properties Atomic/Ionic Radius Ionisation Energy Melting Point Electronegativity No. 1. 2. 3. 4. Element Physical state Ionisation energy Conductivity of element Chloride 4.2. 4.3. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. Conductivity of chloride Hydrolysis of chloride Oxide Hydroxide Complex formation Aqueous solution of ions Electronic configuration Aluminium, Al Metal 𝐴𝑙2 𝐶𝑙6 /𝐴𝑙𝐶𝑙3 Covalent molecule (dimer) Beryllium, Be Other Group 2 Metals Very high High 𝐵𝑒𝐶𝑙4 Covalent molecule (dimer) Ionic crystal Amphoteric 1s22s22p63s23p1 Basic 1s22s2 10.3 USES OF GROUP 2 COMPOUNDS Element Magnesium, Mg Compound Magnesium oxide, MgO Magnesium chloride, MgCl2 Magnesium hydroxide, Mg(OH)2 Agriculture Industry High melting point (2852°C) makes it useful to be used in heating elements, refractory liners in furnaces and in the ceramics and glass industries. Low electrical conductivity makes it a good insulator for electrical cables. Manufacture of cement Textile and paper industries Making fireproof equipment. Important coagulants in food. Medicine Remedy for indigestion, used as antacid and laxatives. Purgative, also used in bath salts to relieve sore muscles and stress. Antiseptics. Magnesium sulphate, MgSO4 (Epsom salts) Calcium, Ca Magnesium borate, B2Mg3O6, magnesium salicylate, C14H10MgO6 and magnesium sulphate Magnesium acetyl salicylate Calcium oxide, CaO (quicklime/lime) Analgesic and to reduce fever. Agricultural lime to neutralise acidic soils. Calcium hydroxide, Ca(OH)2 (slaked lime) Calcium carbonate, CaCO3 (limestone) Calcium sulphate, CaSO4 Fertiliser and soil conditioner. Calcium phosphate, Ca3(PO4)2 Supplement for animal feed and fertiliser. Calcium chloride, CaCl2 Calcium fluoride, CaF2 Major component of cement and mortar. Water softener to remove hardness by reacting with soluble carbonates and bicarbonates to form the insoluble calcium carbonate. Flocculants in water and sewage treatment. Widely used in the food industry because of its low toxicity and mild basic properties, such as sugar industry, processing water for beverages and making of pickles. Exists as limestone, chalk and marble and is very important in the construction industry and in road building. Important coagulants in food. Calcium sulphate naturally occurs as gypsum, (𝐶𝑎𝑆𝑂4 · 2𝐻2𝑂), is used in fireproof plasterboard and ceilings, as common blackboard chalk, as a filler in paint, paper and rubber industries. Anhydrous calcium sulphate is used as desiccant. Desiccant. Make cells and windows for infrared and ultraviolet spectrometers as it is transparent over a range of wavelengths. Used in antacids, toothpaste and chewing gum. Calcium supplement to maintain bone density. Make Plaster of Paris which is used in casts. Strontium, Sr Barium, Ba Strontium oxide, SrO Barium sulphate, BaSO4 Barium carbonate, BaCO3 Barium fluoride, BaF2 Primarily used in colour television cathode ray tubes glass as X-ray absorbing materials Permanent white in paint. As whitener in photographic paper, as filler in paper fibre and polymer. Rat poison Barium fluoride is used for optics in infrared applications. ‘Barium meals’ are used as radiocontrast agents in X-ray imaging of the gastrointestinal tract.