Chapter 20 The Representative Elements

Section 20.1 A Survey of the Representative Elements Copyright © Cengage Learning. All rights reserved 2 Reviewing the Periodic Table Regions  Representative elements:  Groups 1A – 8A (filling s and p orbitals)  Transition metals:  Center of the table (filling d orbitals)

Section 20.1 A Survey of the Representative Elements Copyright © Cengage Learning. All rights reserved 3 Reviewing the Periodic Table Regions  Lanthanides and Actinides:  Listed separately, on the bottom of the table (filling 4f and 5f orbitals)  Metalloids:  Separate metals from nonmetals

Section 20.1 A Survey of the Representative Elements The Atomic Radii of Some Representative Elements (in Picometers)

Section 20.1 A Survey of the Representative Elements Copyright © Cengage Learning. All rights reserved Which should be the larger atom? Why? Na Cl CONCEPT CHECK!

Section 20.1 A Survey of the Representative Elements Which should be the larger atom? Why? Li Cs CONCEPT CHECK!

Section 20.1 A Survey of the Representative Elements Copyright © Cengage Learning. All rights reserved 7 Distribution of the 18 Most Abundant Elements

Section 20.1 A Survey of the Representative Elements Copyright © Cengage Learning. All rights reserved 8 Abundance of Elements in the Human Body

Section 20.2 The Group 1A Elements Alkali Metals: Sources and Methods of Preparation Copyright © Cengage Learning. All rights reserved 9

Section 20.2 The Group 1A Elements Group 1A Oxides Copyright © Cengage Learning. All rights reserved

Section 20.2 The Group 1A Elements Predict the products formed by the following reactants: Na 2 O 2 (s) + H 2 O(l) Copyright © Cengage Learning. All rights reserved 11 → NaOH(aq) + H 2 O 2 (aq) EXERCISE!

Section 20.3 The Chemistry of Hydrogen Hydrides  Binary compounds containing hydrogen:  Ionic hydrides: hydrogen + the most active metals (eg; LiH, CaH 2 )  Covalent hydrides: hydrogen + other nonmetals (eg; H 2 O, CH 4, NH 3 )  Metallic (interstitial) hydrides: transition metal crystals treated with H 2 gas Copyright © Cengage Learning. All rights reserved 12

Section 20.3 The Chemistry of Hydrogen Predict the products formed by the following reactants: LiH(s) + H 2 O(l) Copyright © Cengage Learning. All rights reserved 13 → H 2 (g) + LiOH(aq) EXERCISE!

Section 20.4 The Group 2A Elements Alkaline Earth Metals  Very reactive  Great practical importance:  Human life (Ca and Mg) Copyright © Cengage Learning. All rights reserved 14

Section 20.4 The Group 2A Elements Selected Reactions of Group 2A Elements Copyright © Cengage Learning. All rights reserved 15

Section 20.4 The Group 2A Elements Ion Exchange  Ca 2+ and Mg 2+ are often removed during ion exchange, releasing Na + into solution.  Ion exchange resin – large molecules that have many ionic sites. Copyright © Cengage Learning. All rights reserved 16

Section 20.4 The Group 2A Elements A Schematic Representation of a Typical Cation Exchange Resin Copyright © Cengage Learning. All rights reserved 17

Section 20.5 The Group 3A Elements  Group 3A elements generally show the increase in metallic character in going down the group that is characteristic of the representative elements.  B, Al, Ga, In, Tl Copyright © Cengage Learning. All rights reserved 18

Section 20.5 The Group 3A Elements Some Physical Properties, Sources, and Methods of Preparation Copyright © Cengage Learning. All rights reserved 19

Section 20.5 The Group 3A Elements Some Important Reactions Copyright © Cengage Learning. All rights reserved 20

Section 20.6 The Group 4A Elements  Contains two of the most important elements on earth: carbon and silicon.  Can form four covalent bonds to nonmetals.  CH 4, SiF 4, GeBr 4 Copyright © Cengage Learning. All rights reserved 21

Section 20.6 The Group 4A Elements Some Physical Properties, Sources, and Methods of Preparation Copyright © Cengage Learning. All rights reserved 22

Section 20.6 The Group 4A Elements Some Important Reactions Copyright © Cengage Learning. All rights reserved 23

Section 20.7 The Group 5A Elements  Exhibits varied chemical properties.  N, P, As, Sb, Bi Copyright © Cengage Learning. All rights reserved 24

Section 20.7 The Group 5A Elements Some Physical Properties, Sources, and Methods of Preparation Copyright © Cengage Learning. All rights reserved 25

Section 20.8 The Chemistry of Nitrogen Nitrogen  The great stability of the NΞN bond means that most binary compounds containing nitrogen decompose exothermically to the elements. NO 2 (g) ½N 2 (g) + O 2 (g) ΔH° = –34 kJ N 2 H 4 (g) N 2 (g) + 2H 2 (g) ΔH° = –95 kJ Copyright © Cengage Learning. All rights reserved 26

Section 20.8 The Chemistry of Nitrogen Nitrogen Fixation  The process of transforming N 2 to other nitrogen– containing compounds.  The Haber Process: N 2 (g) + 3H 2 (g) 2NH 3 (g) ΔH° = –92 kJ Copyright © Cengage Learning. All rights reserved 27

Section 20.8 The Chemistry of Nitrogen The Nitrogen Cycle Copyright © Cengage Learning. All rights reserved 28

Section 20.8 The Chemistry of Nitrogen Nitrogen Hydrides  Ammonia, NH 3  Fertilizers  Hydrazine, N 2 H 4  Rocket propellant, manufacture of plastics, agricultural pesticides  Monomethylhydrazine, N 2 H 3 (CH 3 )  Rocket fuels Copyright © Cengage Learning. All rights reserved 29

Section 20.8 The Chemistry of Nitrogen Nitrogen Oxides  Nitrogen in its oxides has oxidation states from +1 to +5.  In other compounds, nitrogen could have oxidation states of - 1 to -3. Compound Oxidation State of N N 2 O+1 NO+2 N 2 O 3 +3 NO 2 +4 HNO 3 +5

Section 20.8 The Chemistry of Nitrogen Nitrogen Oxyacids  Nitric acid, HNO 3  Nitrous acid, HNO 2 Copyright © Cengage Learning. All rights reserved 31

Section 20.8 The Chemistry of Nitrogen The Ostwald Process Copyright © Cengage Learning. All rights reserved 32

Section 20.9 The Chemistry of Phosphorus Allotropes of Phosphorus  White Phosphorus = P 4 (tetrahedral) - very reactive  Black Phosphorus = crystalline structure - much less reactive  Red Phosphorus = amorphous with P 4 chains Copyright © Cengage Learning. All rights reserved 33

Section 20.9 The Chemistry of Phosphorus Allotropes of Phosphorus a) P white b) P black c) P red Copyright © Cengage Learning. All rights reserved 34

Section 20.9 The Chemistry of Phosphorus Phosphorus Oxyacids  Phosphoric acid, H 3 PO 4  Phosphorous acid, H 3 PO 3  Hypophosphorous acid, H 3 PO 2 Copyright © Cengage Learning. All rights reserved 35

Section The Group 6A Elements  O, S, Se, Te, Po  Although in Group 6A there is the usual tendency for metallic properties to increase going down the group, none of the Group 6A elements behaves as a typical metal.  Can form covalent bonds with other nonmetals. Copyright © Cengage Learning. All rights reserved 36

Section The Group 6A Elements Some Physical Properties, Sources, and Methods of Preparation Copyright © Cengage Learning. All rights reserved 37

Section The Chemistry of Oxygen Oxygen  O 2 makes up 21% of the Earth’s atmosphere.  O 3 (ozone) exists naturally in the upper atmosphere of the Earth.  Ozone layer absorbs UV light and acts as a screen to prevent this radiation from penetrating to the Earth’s surface.  Scientists have become concerned that Freons and nitrogen dioxide are promoting the destruction of the ozone layer. Copyright © Cengage Learning. All rights reserved 38

Section The Chemistry of Oxygen Ozone

Section The Chemistry of Sulfur  Sulfur is found in nature both in large deposits of the free element and in ores such as galena, cinnabar, pyrite, gypsum, epsomite, and glauberite. Copyright © Cengage Learning. All rights reserved 40

Section The Chemistry of Sulfur Frasch Process Copyright © Cengage Learning. All rights reserved 41

Section The Chemistry of Sulfur Aggregates of Sulfur Copyright © Cengage Learning. All rights reserved 42

Section The Chemistry of Sulfur Sulfur Oxide Reactions 2SO 2 (g) + O 2 (g) 2SO 3 (g) SO 2 (g) + H 2 O(l) H 2 SO 3 (aq) SO 3 (g) + H 2 O(l) H 2 SO 4 (aq) Copyright © Cengage Learning. All rights reserved 43

Section The Group 7A Elements Halogens  All nonmetals: F, Cl, Br, I, At  Because of their high reactivities, the halogens are not found as free elements in nature. They are found as halide ions (X – ) in various minerals and in seawater. Copyright © Cengage Learning. All rights reserved 44

Section The Group 7A Elements Trends in Selected Physical Properties Copyright © Cengage Learning. All rights reserved 45

Section The Group 7A Elements Some Physical Properties, Sources, and Methods of Preparation Copyright © Cengage Learning. All rights reserved 46

Section The Group 7A Elements Preparation of Hydrogen Halides H 2 (g) + X 2 (g) 2HX(g)  When dissolved in water, the hydrogen halides behave as acids, and all except hydrogen fluoride are completely dissociated. Copyright © Cengage Learning. All rights reserved 47

Section The Group 7A Elements Halogen Oxyacids and Oxyanions  All halogens except fluorine combine with various numbers of oxygen atoms to form a series of oxyacids.  The strengths of these acids vary in direct proportion to the number of oxygen atoms attached to the halogen, with the acid strength increasing as more oxygens are added. Copyright © Cengage Learning. All rights reserved 48

Section The Group 7A Elements The Known Oxyacids of the Halogens Copyright © Cengage Learning. All rights reserved 49

Section The Group 8A Elements Noble Gases  Filled s and p valence orbitals  He and Ne form no compounds.  Kr and Xe have been observed to form chemical compounds: Xe(g) + 2F 2 (g) XeF 4 (s) [6 atm, 400°C] XeF 6 (s) + 3H 2 O(l) XeO 3 (aq) + 6HF(aq) Copyright © Cengage Learning. All rights reserved 50

Section The Group 8A Elements Selected Properties Copyright © Cengage Learning. All rights reserved 51

Section The Group 8A Elements Which of the following groups is the most reactive? a) Group 1A Elements b) Group 5A Elements c) Group 6A Elements d) Group 8A Elements Copyright © Cengage Learning. All rights reserved 52 CONCEPT CHECK!

Section The Group 8A Elements Which of the following groups does not contain at least one element that forms compounds with oxygen? a) Group 4A Elements b) Group 5A Elements c) Group 6A Elements d) Group 7A Elements e) All of these groups contain at least one element that forms compounds with oxygen. Copyright © Cengage Learning. All rights reserved 53 CONCEPT CHECK!