Alkaline Earth Metals Beryllium Magnesium Strontium Radium Barium Calcium

Alkaline Earth Metals Why were these elements called “alkaline earth metals”? What do you think about the uses of these elements commonly?

Properties Beryllium Magnesium Calcium Earth`s crust abundance 1.9x10 -4 2.9 5 Electron configuration [He]2s2 [Ne]3s2 [Ar]4s2 Melting point (oC) 1287 650 842 Boiling point (oC) 2469 1090 1484 Density 1.85 1.74 1.55 Common oxidation num. +2 Physical State solid Color grey white White

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.

Characteristic Flame Colors of Alkaline Earth Metals Calcium Strontium Barium Magnesium

All isotopes are radioactive Minerals of Some Alkaline Earth Metals Beryllium Calcium Barium Beryl, Be3Al2(SiO3)6 Limestone (marble), CaCO3 Barytes, BaSO4 Magnesium Gypsum, CaSO4.2H2O Witherite, BaCO3 Dolomite, CaCO3. MgCO3 Fluorite, CaF2 Radium Carnallite, KCI.MgCI2.6H2O Strontium All isotopes are radioactive Epsom salt, MgSO4.7H2O Celestite, SrSO4 Strontianite, SrCO3

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) + 2H2O(l) → Ca+2(aq) + 2OH-(aq) + H2(g) Mg (s) + 2H2O(l) → Mg(OH)2(s) + H2(g) 2Mg (s) + O2(g) → 2MgO(s) Mg (s) + H2(g) → MgH2(s) Ca (s) + 2HCI(aq) → CaCl2 + H2(g) Be (s) + 2HCI(aq) → BeCI2 + H2(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.

Calcium Oxide, CaO Obtained by heating calcium carbonate (limestone) at 900°C. CaCO3(s) → CaO(s) + CO2(g) Calcium Carbonate, CaCO3 It forms by evolving CO2 gas from Ca(OH)2 solution.

Calcium Carbide, CaC2 Small gray solid pieces Used widely in industry Prepared by the reaction of calcium oxide (lime) and coke. CaO(s) + 3C(s) ↔ CaC2(s) + CO (g) CaC2(s) + 2H2O(l) → C2H2(g) + Ca(OH)2(s)

Calcium Sulfate, CaSO4 CaSO4.2H2O : Gypsum CaSO4.1/2H2O : Plaster of Paris Gypsum is a white substance and used for fabrication into wallboard.

Uses Beryllium 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.

Uses Magnesium 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.

Calcium Compounds Construction materials, bleaching agents. CaO in the production of some chemicals, steel, glass, paper and sugar. CaC2 is used to produce acetylene gas for welding. In fertilizers and toothpaste

Barium and Its 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 BaSO4 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 BaSO4 in water is very low, its poisonous effect disappears.

Strontium The salts of strontium in signal rockets and fireworks to produce red light. Nuclear batteries.

Radium In self luminous paints and in radiotherapy. As a neutron source. On luminous watch dials.