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Group Trends Hydrogen Hydrogen is a unique element. Most often occurs as a colorless diatomic gas, H2. It can either gain another electron to form the hydride ion, H-, or lose its electron to become H+: 2Na(s) + H2(g) 2NaH(s) 2H2(g) + O2(g) 2H2O(g) H+ is a proton. The aqueous chemistry of hydrogen is dominated by H+(aq).
Group Trends for the Active Metals Group 1A: The Alkali Metals Alkali metals are all soft, silvery, very reactive. Chemistry dominated by the loss of their single s electron: M M+ + e- Alkali metals react with water to form MOH and hydrogen gas: 2M(s) + 2H2O(l) 2MOH(aq) + H2(g)
Common Alkali Metals • Lithium (Li) • battery anode material • used as drugs to treat manic-depressive disorders. (Lithiated Bib-Label Soda) • Sodium (Na) • “Common/Table salt" (sodium chloride, NaCl), "soda ash" (sodium carbonate, Na2CO3), "baking soda" (sodium bicarbonate, NaHCO3, "bicarb"), and "caustic soda" (sodium hydroxide, NaOH), are important to the paper, glass, soap, textile, petroleum, chemical, and metal industries • sodium vapour is used in lamps for street lighting
Group Trends for the Active Metals Group 2A: The Alkaline Earth Metals Alkaline earth metals are harder and more dense than the alkali metals. The chemistry is dominated by the loss of two s electrons: M M2+ + 2e-. Mg(s) + Cl2(g) MgCl2(s) 2Mg(s) + O2(g) 2MgO(s) Be does not react with water. Mg will only react with steam. Ca onwards: Ca(s) + 2H2O(l) Ca(OH)2(aq) + H2(g)
Romans used mortars containing lime (CaO) mixed with sand; Egyptians used gypsum (CaSO4*2H2O) in plasters for their tombs. • Radium, from pitchblende (Curies, 1898)
Magnesium • used in flares and pyrotechnics, including incendiary bombs. It was used in flash photography, • it is lighter than aluminum, and is used in alloys used for aircraft, car engine casings, and missile construction • Calcium • quicklime (CaO) is made by heating limestone (CaCO3) and changes into slaked lime, Ca(OH)2, on the addition of water. It is a cheap base for the chemical industry with many uses. • calcium from limestone is a component of Portland cement. Mixed with sand it hardens as mortar and plaster while taking up carbon dioxide from the air • the solubility of the carbonate in water containing carbon dioxide results in stalactites and stalagmites and hardness in water.
Boron group • Boron • borax, Na2B4O7.10H2O is a water softener in washing powders • Aluminum • Cans, foils, utensils, industrial applications where a strong, light, easily constructed material is needed (eg. Space/aircraft) • the oxide, alumina, occurs naturally as ruby, sapphire, corundum, and emery, and is used in glass making and refractories
Preview: Carbon and its group Graphite Buckminsterfullerene (Buckyball) Diamond Silicon * silica, as sand, is a principal ingredient of glass, a material with excellent mechanical, optical, thermal, and electrical properties * computer chips, and other important electronic components
Nitrogen Group • Nitrogen • N2: most abundant gas in atmosphere • Ammonia!, Liquid Nitrogen • Phosphorus: • First isolated from urine; glowed in dark (phos: light; phoros:bringing) • used in the manufacture of safety matches, pyrotechnics, incendiary shells, smoke bombs, tracer bullets, etc. • Fertilizers and pesticides
Group Trends for Selected Nonmetals Group 6A: The Oxygen Group (Chalcogens) As we move down the group the metallic character increases (O2 is a gas, Te is a metalloid, Po is a metal). There are two important forms of oxygen: O2 and ozone, O3. Ozone can be prepared from oxygen: 3O2(g) 2O3(g) H = +284.6 kJ. Ozone is pungent and toxic.
Group Trends for Selected Nonmetals Group 6A: The Oxygen Group Oxygen (or dioxygen, O2) is a potent oxidizing agent since the O2- ion has a noble gas configuration. There are two oxidation states for oxygen: 2- (e.g. H2O) and 1- (e.g. H2O2). SULFUR Sulfur is another important member of this group. Most common form of sulfur is yellow S8. Sulfur tends to form S2- in compounds (sulfides). *Sulfur: “brimstone”; GUNPOWDER: sulfur, KNO3, charcoal
Group Trends for Selected Nonmetals Group 7A: The Halogens The chemistry of the halogens is dominated by gaining an electron to form an anion: X2 + 2e- 2X-. Fluorine is one of the most reactive substances known: 2F2(g) + 2H2O(l) 4HF(aq) + O2(g) H = -758.7 kJ. All halogens consists of diatomic molecules, X2.
Group Trends for Selected Nonmetals Group 8A: The Noble Gases These are all nonmetals and monatomic. They are notoriously unreactive because they have completely filled s and p sub-shells. In 1962 the first compound of the noble gases was prepared: XeF2, XeF4, and XeF6. Another example: KrF2
Chemistry in Action: Discovery of the Noble Gases Sir William Ramsay
For more information, visit • http://www.chemicalelements.com • http://www.webelements.com