lecture6 - Periodic trends and reactivity Chem 1A Lecture...

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Unformatted text preview: Periodic trends and reactivity Chem 1A Lecture 6: Chem 1A Trends in reactivity Groups IIIA, IVA, VA, and VIA have more diversity because they include metals, nonmetals, and metalloids IIA: [x]ns 2 IA: [x]ns 1 VIIA: [x]ns 2 np 5 VIIIA: [x]ns 2 np 6 Group IIA The group II A metals are less reactive than group IA, but follow the same kinds of trends. magnesium metal Electron configuration: [x]ns 2 , n 2 Easily form +2 ions. Be does not react with water, Mg reacts with steam, while Ca, Sr, and Ba can react with liquid water. Mg (s) + 2 H 2 O (g) Mg(OH) 2 (aq) + H 2 (g) Group IIA Mg can be burned in air to make magnesium oxide. This produces a bright light often used in fireworks and flares. burning magnesium metal Mg (s) + O 2 (g) 2 MgO(s) Calcium in bones and teeth Bones and teeth are made of hydroxyapatite, a calcium-containing mineral. Ca 5 (PO 4 ) 3 OH Tooth decay While Ca 5 (PO 4 ) 3 OH is essentially insoluble in water, it is slightly soluble in acidic solution: Ca 5 (PO 4 ) 3 OH (s) + 4H 3 O + (aq) 5Ca 2+ (aq) + 3 HPO 4 2- (aq) + 5 H 2 O (l) bacteria produce acid hydroxyapatite dissolves Metalloids Metalloids have some properties of metals and nonmetals. They form amphoteric oxides and often behave as semiconductors. n-type and p-type semiconductors silicon wafer We use semiconductors every day Group IIIA Electron configuration: [x]ns 2 np 1 , n 2 The other metals can form +3 or +1 ions. Aluminum forms only +3 ions. Boron is a metalloid Boron fireworks The rest of the group IIIA elements are metals. Group IIIA elements also make molecular compounds. Group IIIA - aluminum oxide Aluminum reacts with oxygen to make aluminum oxide. Al 2 O 3 is used as an abrasive. Sapphires and rubies come from the mineral corundum (Al 2 O 3 with impurities). Al is difficult to weld because of its oxide layer 2 Al (s) + 3 O 2 (g) 2 Al 2 O 3 (s) Group IIIA Aluminum reacts with acid to liberate hydrogen gas....
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This note was uploaded on 02/25/2012 for the course CHEM 1A 40030 taught by Professor Borovick during the Fall '10 term at UC Irvine.

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lecture6 - Periodic trends and reactivity Chem 1A Lecture...

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