Why were these elements called “alkaline earth metals”? What do you think about the uses of these elements commonly? Alkaline Earth Metals
The word “earth” was used for the oxides of group 2A by the ancient scientists. Alkaline earth metals, after the alkali metals, are secondary metals with strong metallic properties. The group 2A elements are less active than those of 1A, but more active than those of group 3A. Except Be, all form ionic compounds. Be forms mostly covalent compounds.
The atomic radius increases from top to bottom. The melting point, boiling point and the hardness of the elements decrease from top to bottom. Beryllium is the hardest alkaline earth metal Barium is the softest alkaline earth metal. Malleable and ductile. Excess Mg +2 and Ca +2 in water means that it is hard.
Chemical Properties They are Covered by their oxides when they are exposed to air. Burn in air with bright flame. Activity of the metals increases from Be to Ba. Reactions of Ca, Sr and Ba are easy with water. Reactions of Be and Mg with water are difficult.
Chemical Properties Ca (s) + 2H 2 O(l) → Ca +2 (aq) + 2OH - (aq) + H 2 (g) Mg (s) + 2H 2 O(l) → Mg(OH) 2 (s) + H 2 (g) 2Mg (s) + O 2 (g) → 2MgO(s) Mg (s) + H 2 (g) → MgH 2 (s) Ca (s) + 2HCI(aq) → CaCl 2 + H 2 (g) Be (s) + 2HCI(aq) → BeCI 2 + H 2 (g) All oxides and hydroxides of alkaline earth metals show basic properties. Oxides and its hydroxides of beryllium show amphoteric properties.
Compounds Ionic Have high melting and boiling points. Thermally stable. Less soluble in water than those of 1A metals. Solubility of salts increase from Be to Ba.
Obtained by heating calcium carbonate (limestone) at 900°C. CaCO 3 (s) → CaO(s) + CO 2 (g) Calcium Oxide, CaO Calcium Carbonate, CaCO 3 It forms by evolving CO 2 gas from Ca(OH) 2 solution.
Small gray solid pieces Used widely in industry Prepared by the reaction of calcium oxide (lime) and coke. CaO(s) + 3C(s) ↔ CaC 2 (s) + CO (g) CaC 2 (s) + 2H 2 O(l) → C 2 H 2 (g) + Ca(OH) 2 (s) Calcium Carbide, CaC 2
CaSO 4.2H 2 O : Gypsum CaSO 4.1/2H 2 O : Plaster of Paris Gypsum is a white substance and used for fabrication into wallboard. Calcium Sulfate, CaSO 4
Uses Very light element To prepare some special alloys. 2% Be in Cu alloy in springs. Making glass for X-ray tubes. In the aerospace industry. Beryllium
Uses Light metal Production of planes, missiles Some light household items. Flash in photography Magnesium
To increase the hardness, durability and resistance to corrosion of alloys. Additive in rocket fuels and signal rockets. Mg(OH) 2 is used as a stomach antacid. Magnesium
Construction materials, bleaching agents. CaO in the production of some chemicals, steel, glass, paper and sugar. CaC 2 is used to produce acetylene gas for welding. In fertilizers and toothpaste Calcium Compounds
Ba is used as a gas absorbent in vacuum tubes. The alloys of Ba with Ni donate electrons so used in vacuum tubes and in ignitors and spark plugs. Barium nitrate and barium chlorate are used to obtain green light in fireworks. Barium and Its Compounds
BaSO 4 is used to take the photos of stomach and intestines. Ba does not allow X-rays to pass like all elements with large atomic number. The Ba +2 ion is toxic, but since the solubility of BaSO 4 in water is very low, its poisonous effect disappears. Barium and Its Compounds
The salts of strontium in signal rockets and fireworks to produce red light. Nuclear batteries. Strontium
In self luminous paints and in radiotherapy. As a neutron source. On luminous watch dials. Radium