1. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Chapter 7 Periodic Properties of the Elements Chemistry, The Central Science, 11th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten John D. Bookstaver St. Charles Community College Cottleville, MO

2. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Overview of Periodic Trends Why and how show we study trends in the periodic table? Focus on valence electrons  understand and predict reactivity of elements

3. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Overview of Periodic Trends 1.Trends within the periodic table can be qualitatively understood and explained using Coulomb’s law, the shell model, and the concept of shielding/effective nuclear charge. Key concept: Effective nuclear charge  effects on the valence electron(s) a) First ionization energy b) Atomic and ionic radius c) Electronegativity (in bonding chapters) d) Typical ionic charges

4. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Overview of Periodic Trends Be able to predict and explain the trends, using effective nuclear charge (and the shielding effect) and atomic structure. Other ways to describe these periodic trends incorporate the use of PES data with ionization energy, an application of Coulomb’s Law. (more on this later)

5. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Overview of Periodic Trends 2.Effects on the properties of metals, nonmetals and metalloids  group trends in terms of reactions

6. Periodic Properties of the Elements Coulomb’s Law The force between two charged particles is proportional to the magnitude of the two charges (q 1 and q 2 ), and inversely proportional to the square of the distance, r, between them. If the charges are the same, they repel each other. If the charges are opposite (protons vs. electrons), they attract each other. © 2009, Prentice-Hall, Inc.

7. Periodic Properties of the Elements Coulomb’s Law F = k Q 1 Q 2 r 2 In terms of potential energy, E = k Q 1 Q 2 r Physics: Whenever you move a particle in a direction it doesn’t want to go in a field (e.g. electrical or gravitational), you give it PE proportional to the distance you move it. (from Mr. Lapp) We will apply Coulomb’s Law qualitatively © 2009, Prentice-Hall, Inc.

8. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Effective Nuclear Charge In a many-electron atom, electrons are both attracted to the nucleus and repelled by other electrons. The nuclear charge that an electron experiences depends on both factors.

9. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Effective Nuclear Charge a way to quantify the shielding effect The effective nuclear charge, Z eff, is found this way: Z eff = Z − S where Z is the atomic number and S is a screening constant, usually close to the number of inner electrons.

10. Periodic Properties of the Elements Shielding Effect The position of a valence electron and the ability to remove it from an atom are related to the number of protons in the nucleus the extent to which the valence electron is shielded from the positively-charged nucleus by the negatively-charged core electrons © 2009, Prentice-Hall, Inc.

11. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. What Is the Size of an Atom? The bonding atomic radius is defined as one-half of the distance between covalently bonded nuclei.

12. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sizes of Atoms Bonding atomic radius tends to… …decrease from left to right across a row (due to increasing Z eff ). …increase from top to bottom of a column (due to increasing value of n). We can also describe this trend using the shielding effect.

13. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sizes of Ions Ionic size depends upon: –The nuclear charge. –The number of electrons. –The orbitals in which electrons reside.

14. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sizes of Ions Cations are smaller than their parent atoms. –The outermost electron is removed and repulsions between electrons are reduced.

15. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sizes of Ions Anions are larger than their parent atoms. –Electrons are added and repulsions between electrons are increased.

16. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sizes of Ions Ions increase in size as you go down a column. –This is due to increasing value of n. –and the larger shield of core electrons

17. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sizes of Ions In an isoelectronic series, ions have the same number of electrons. Ionic size decreases with an increasing nuclear charge.

18. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Ionization Energy ionization energy = the amount of energy required to remove an electron from the ground state of a gaseous atom or ion. –The first ionization energy is the energy required to remove the first electron. –The second ionization energy is that energy required to remove a second electron, etc.

19. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Ionization Energy It requires more energy to remove each successive electron. When all valence electrons have been removed, the ionization energy takes a quantum leap.

20. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Trends in First Ionization Energies As one goes down a column, less energy is required to remove the first electron. –For atoms in the same group, Z eff is essentially the same, but the valence electrons are farther from the nucleus. –Increased shielding effect down the group, resulting in more exposure of the valence electrons

21. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Trends in First Ionization Energies Generally, as one goes across a row, it gets harder to remove an electron. –As you go from left to right, Z eff increases. –Same number of core electrons = same size shield as you go from left to right, BUT increasing attraction by the nucleus for the valence electrons makes it harder to remove an electron.

22. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Trends in First Ionization Energies However, there are two apparent discontinuities in this trend.

23. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Trends in First Ionization Energies The first occurs between Groups IIA and IIIA. In this case the electron is removed from a p-orbital rather than an s-orbital. –The electron removed is farther from nucleus. –There is also a small amount of repulsion by the s electrons.

24. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Trends in First Ionization Energies The second occurs between Groups VA and VIA. –The electron removed comes from doubly occupied orbital. –Repulsion from the other electron in the orbital aids in its removal.

25. Periodic Properties of the Elements Photoelectron Spectroscopy (PES) Quantifiable application of the photoelectric effect If light shining on a material (especially a metal) has sufficient energy it is able to eject electrons from that material (Each photon: E=h, see Ch. 6) Photoelectron spectroscopy determines the amount of energy needed to do so. © 2009, Prentice-Hall, Inc.

26. Periodic Properties of the Elements Photoelectron Spectroscopy (PES) Measurement of these energies  deduce the structure of the atom Intensity of the signal  number of electrons at that energy level Note: energy is measured in eV or MJ/mole electrons © 2009, Prentice-Hall, Inc.

27. Periodic Properties of the Elements Example of PES © 2009, Prentice-Hall, Inc. From Adrian Dingle’s blog, Jan. 29, 2013 http://www.adriandingleschemistrypages.com/ap/summary-of-additions-to-new-ap-chemistry-curriculum-part-1-pes/ Generated by the simulation at; http://www.chem.arizona.edu/chemt/Flash/photoelectron.htmlhttp://www.chem.arizona.edu/chemt/Flash/photoelectron.html What does this mean? Another way to view ionization energy

28. Periodic Properties of the Elements PES Example Questions © 2009, Prentice-Hall, Inc. From Adrian Dingle’s blog: http://www.adriandingleschemistrypages.com/ap/summary-of-additions-to-new-ap-chemistry-curriculum-part-1-pes/ If the question flagged Mg as the element in question: a.Which peak in the spectrum represents electrons that are closest to the nucleus? a.What is the relevance of the relative height of the peaks at 5.31 and 9.07 eV? a.Why is there such a large difference in energy between the peaks at 0.74, 5.31 and 9.07 eV and the peak at 126 eV?

29. Periodic Properties of the Elements PES Example Questions © 2009, Prentice-Hall, Inc. From Adrian Dingle’s blog: http://www.adriandingleschemistrypages.com/ap/summary-of-additions-to-new-ap-chemistry-curriculum-part-1-pes/ If the question flagged Mg as the element in question: a.Which peak in the spectrum represents electrons that are closest to the nucleus? 126 eV a.What is the relevance of the relative height of the peaks at 5.31 and 9.07 eV? different numbers of electrons a.Why is there such a large difference in energy between the peaks at 0.74, 5.31 and 9.07 eV and the peak at 126 eV? 126 eV – 1s 2, biggest Coulomb effect

30. Periodic Properties of the Elements PES Example Questions © 2009, Prentice-Hall, Inc. From Adrian Dingle’s blog: http://www.adriandingleschemistrypages.com/ap/summary-of-additions-to-new-ap-chemistry-curriculum-part-1-pes/ If the question did not flag Mg as the element in question: a.Assuming that the PES data shows ALL the electrons present in the atom, identify the element. a.Still applying the assumption above, which specific electrons are associated with the peak at 126 eV? b.What does a relatively low value of energy tell you about the relative position of the electrons within any atom?

31. Periodic Properties of the Elements PES Example Questions © 2009, Prentice-Hall, Inc. From Adrian Dingle’s blog: http://www.adriandingleschemistrypages.com/ap/summary-of-additions-to-new-ap-chemistry-curriculum-part-1-pes/ If the question did not flag Mg as the element in question: a.Assuming that the PES data shows ALL the electrons present in the atom, identify the element. Mg a.Still applying the assumption above, which specific electrons are associated with the peak at 126 eV? 1s 2 – closest to the nucleus a.What does a relatively low value of energy tell you about the relative position of the electrons within any atom? They are the valence electron(s)

32. Periodic Properties of the Elements PES Example Questions © 2009, Prentice-Hall, Inc. From Adrian Dingle’s blog: http://www.adriandingleschemistrypages.com/ap/summary-of-additions-to-new-ap-chemistry-curriculum-part-1-pes/ Mg is found in group 2 and period 3 of the periodic table. Use this information to answer the following questions: a.Predict the full electronic configuration of Mg using s,p,d,f notation. b.Use your answer in a to predict the relative heights of the four peaks found in the PES plot for Mg.

33. Periodic Properties of the Elements PES Example Questions © 2009, Prentice-Hall, Inc. From Adrian Dingle’s blog: http://www.adriandingleschemistrypages.com/ap/summary-of-additions-to-new-ap-chemistry-curriculum-part-1-pes/ Mg is found in group 2 and period 3 of the periodic table. Use this information to answer the following questions: a.Predict the full electronic configuration of Mg using s,p,d,f notation. 1s 2 2s 2 2p 6 3s 2 a.Use your answer in (a) to predict the relative heights of the four peaks found in the PES plot for Mg. 1s 2, 2s 2 and 3s 2 peaks will be the same height. 2p 6 peak will be about 3X higher.

34. Periodic Properties of the Elements Recommended Supplemental PES Material Coulomb’s Law and AP Chem: Paul Andersen http://www.bozemanscience.com/ap- chem-004-coulombs-law/http://www.bozemanscience.com/ap- chem-004-coulombs-law/ PES in more depth: UC-Davis Chemwiki http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectr oscopy/Photoelectron_Spectroscopy/Photoelectron_Sp ectroscopy%3A_Theory © 2009, Prentice-Hall, Inc.

35. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Electron Affinity Electron affinity is the energy change accompanying the addition of an electron to a gaseous atom: Cl + e −  Cl −

36. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Ionization Energy vs. Electron Affinity Ionization energy: how much does it cost to remove an electron? –Always positive (+kJ) Electron affinity: What is the energy change when an electron is added to an atom? –Positive or negative (+kJ or –kJ) Together ionization energy and electron affinity  electronegativity  bonding and reactivity

37. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Properties of Metal, Nonmetals, and Metalloids

38. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Metals They tend to be lustrous, malleable, ductile, and good conductors of heat and electricity.

39. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Metals Compounds formed between metals and nonmetals tend to be ionic. Metal oxides tend to be basic when dissolved in water.

40. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Reactions of Metal Oxides Most metal oxides are basic: Metal oxide + water  metal hydroxide (synthesis reaction) Na 2 O (s) + H 2 O (l)  2NaOH (aq)

41. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Reactions of Metal Oxides Metal oxides are able to react with acids to form salts and water: Metal oxide + acid  salt + water MgO (s) + 2HCl (aq)  MgCl 2(aq) + H 2 O (l)

42. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Practice Exercise 7.8 Write the balanced chemical equation for the reaction between copper (II) oxide and sulfuric acid.

43. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Metals versus Nonmetals Differences between metals and nonmetals tend to revolve around these properties.

44. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Metals versus Nonmetals Metals tend to form cations (are oxidized), including oxides (think rust). Nonmetals tend to form anions (are reduced).

45. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Nonmetals These are dull, brittle substances that are poor conductors of heat and electricity. They tend to gain electrons in reactions with metals to acquire a noble gas configuration.

46. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Nonmetals Substances containing only nonmetals are molecular compounds. Most nonmetal oxides are acidic when dissolved in water.

47. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Nonmetals Seven nonmetallic elements exist as diatomic molecules under ordinary conditions: H 2(g), N 2(g), O 2(g), F 2(g), Cl 2(g), Br 2(l), I 2(s) Remember the “7” rule.

48. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Reactions - Nonmetals When nonmetals react with metals, nonmetals tend to gain electrons: Metal + nonmetal  salt 2Al (s) + 3Br 2(l)  2AlBr 3 (s)

49. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Reactions - Nonmetals Most nonmetal oxides are acidic when dissolved in acid: Nonmetal oxide + water  acid (synthesis) P 4 O 10(s) + 6H 2 O (l)  4H 3 PO 4(aq) CO 2(g) + H 2 O (l)  H 2 CO 3(aq)

50. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Reactions - Nonmetals Nonmetal oxides react with bases to form salts and water: Nonmetal oxide + base  salt + water CO 2(g) + 2NaOH (aq)  Na 2 CO 3(aq) + H 2 O (l)

51. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sample Exercise 7.9 (p. 256) Write the balanced chemical equations for the reactions of solid selenium dioxide with a) water b) aqueous sodium hydroxide

52. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Practice Exercise 7.9 Write the balanced chemical equation for the reaction of solid tetraphosphorus hexoxide with water.

53. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Metalloids These have some characteristics of metals and some of nonmetals. For instance, silicon looks shiny, but is brittle and fairly poor conductor.

54. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Group Trends

55. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Alkali Metals Alkali metals are soft, metallic solids. The name comes from the Arabic word for ashes.

56. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Alkali Metals They are found only in compounds in nature, not in their elemental forms. They have low densities and melting points. They also have low ionization energies.

57. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Alkali Metals Reactions Alkali metals react with hydrogen to form hydrides. In hydrides, the hydrogen is present as H –, called the hydride ion. 2M (s) + H 2(g)  2MH (s)

58. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Alkali Metals Alkali metals react with water to form MOH and hydrogen gas: e.g. Na (s) + H 2 O (l)  NaOH (aq) + H 2(g)

59. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Alkali Metals Reactions Alkali metals produce different oxides when reacting with O 2 : 4Li (s) + O 2(g)  2Li 2 O (s) (oxide) 2Na (s) + O 2 (g)  Na 2 O 2(s) (peroxide) K (s) + O 2 (g)  KO 2(s) (superoxide)

60. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Alkali Metals Alkali metals (except Li) react with oxygen to form peroxides. K, Rb, and Cs also form superoxides: K + O 2  KO 2 They produce bright colors when placed in a flame.

61. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sample Exercise 7.10 (p. 279) Write balanced chemical equations that predict the reactions of cesium metal with a)Cl 2(g) b)H 2 O (l) c)H 2(g)

62. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Practice Exercise 7.10 Write a balanced chemical equation that predicts the products of the reaction between potassium metal and elemental sulfur (S 8 ).

63. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Alkaline Earth Metals Alkaline earth metals have higher densities and melting points than alkali metals. Their ionization energies are low, but not as low as those of alkali metals.

64. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Alkaline Earth Metals Reactions Their chemistry is dominated by the loss of two s electrons: M  M 2+ + 2e – Mg (s) + Cl 2(g)  MgCl 2(s) 2Mg (s) + O 2(g)  2MgO (s) (remember last year’s Reactions labs – white flame?

65. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Alkaline Earth Metals Reactivity increases down the group. Beryllium does not react with water and magnesium reacts only with steam, but the others react readily with water. Thursday’s lab

66. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Hydrogen Hydrogen is a unique element, most often occurs as a colorless diatomic gas, H 2. Reactions between hydrogen and nonmetals can be very exothermic: 2H 2(g) + 2O 2(g)  2H 2 O (l) ∆H o = –571.7 kJ

67. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Hydrogen It can either gain another electron to form the hydride ion, H –, or lose its electron to become H + : 2Na (s) + H 2(g)  2NaH (s) 2H 2(g) + O 2(g)  2H 2 O (l)

68. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Hydrogen H + is a proton. The aqueous chemistry of hydrogen is dominated by H + (aq). (acids – next semester)

69. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Group 6A Oxygen, sulfur, and selenium are nonmetals. Tellurium is a metalloid. The radioactive polonium is a metal.

70. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Oxygen There are two allotropes of oxygen: –O2–O2 –O 3, ozone There can be three anions: –O 2−, oxide –O 2 2−, peroxide –O 2 1−, superoxide It tends to take electrons from other elements (oxidation).

71. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sulfur Sulfur is a weaker oxidizer than oxygen. The most stable allotrope is S 8, a ringed molecule.

72. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Group 7A: Halogens The halogens are prototypical nonmetals. The name comes from the Greek words halos and gennao: “salt formers”. All halogens are diatomic: X 2.

73. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Group 7A: Halogens The chemistry of the halogens is dominated by gaining an electron to form an anion: X 2 + 2e –  2X – Fluorine is one of the most reactive substances known: 2F 2(g) + 2H 2 O (l)  4HF (aq) + O 2(g)  H = –758.9 kJ

74. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Group 7A: Halogens They have large, negative electron affinities. –Therefore, they tend to oxidize other elements easily. They react directly with metals to form metal halides. Chlorine is added to water supplies to serve as a disinfectant

75. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Group 7A: Halogens Chlorine is added to water supplies to serve as a disinfectant e.g. swimming pools: Cl 2(g) + H 2 O (l)  HCl (aq) + HOCl (aq)

76. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Group 8A: Noble Gases The noble gases have astronomical ionization energies. Their electron affinities are positive. –Therefore, they are relatively unreactive. They are found as monatomic gases.

77. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Group 8A: Noble Gases Xe forms three compounds: –XeF 2 –XeF 4 (at right) –XeF 6 Kr forms only one stable compound: –KrF 2 The unstable HArF was synthesized in 2000.

78. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sample Integrative Exercise 7 (p. 285) The element bismuth (Bi, atomic number 83) is the heaviest member of group 5A. A salt of the element, bismuth subsalicylate, is the active ingredient in Pepto-Bismol, an over-the-counter medication for gastric distress. 1.The covalent atomic radii of thallium (Tl) and lead (Pb) are 1.48 Å and 1.47 Å, respectively. Using these values and what you know about trends in atomic radii, predict the covalent atomic radius of the element bismuth. Explain your answer. 2.What accounts for the general increase in atomic radius going down the group 5A elements? 3.Another major use of bismuth has been as an ingredient in low-melting metal alloys, such as those used in fire sprinkler systems and in typesetting. The element itself is a brittle white crystalline solid. How do these characteristics fit with the fact that bismuth is in the same periodic group with such nonmetallic elements as nitrogen and phosphorus?

79. Periodic Properties of the Elements © 2009, Prentice-Hall, Inc. Sample Integrative Exercise 7 (p. 285) 4.Bi 2 O 3 is a basic oxide. Write a balanced equation for its reaction with dilute nitric acid. If 6.77 g of Bi 2 O 3 is dissolved in dilute acidic solution to make up 500 mL of solution, what is the molarity of the Bi 3+ ion? 5. 209 Bi is the heaviest stable isotope of any element. How many protons and neutrons are present in this nucleus? 6.The density of Bi at 25 o C is 9.808 g/cm 3. How many Bi atoms are present in a cube of the element that is 5.00 cm on each edge? How many moles of the element are present?