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Periodic Trends

Learn about the characteristics of metals, nonmetals, and metalloids and how they relate to trends in atomic radius, ionization energy, and electron affinity.

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Periodic Trends

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  1. Periodic Trends Section 8.6-8.8

  2. Objectives • Review the characteristics in metals, nonmetals, and metalloids • Relate these characteristics to trends in atomic radius/ ionization energy/electron affinity

  3. Key Terms • Metallic character • Nonmetallic character

  4. Metals, Nonmetals, Metalloids

  5. Metallic Character • Degree to which an element exhibits the physical and chemical properties of a metal.

  6. Metals • Lustrous, malleable, ductile, good conductors • All solids except liquid Hg

  7. Metals • LOW Ionization energy form positive ions easily • Ionization energy decreases as metallic character increases

  8. Ionic Compounds • Form between metal and nonmetal • Metal oxides are bases • Metal oxide + H2O  metal hydroxide [7.9] Ionizes in water, freeing up the metal and O • Metal oxide + acid  salt + H2O [7.12]

  9. Nonmetals • Dull, brittle, nonconductors (insulators). • Gases: H, N, O, F, Cl, noble gases • Liquid: Br • KNOW PHYSICAL STATES OF ALL THE ELEMENTS!!

  10. Nonmetals • HIGH electron affinities  gain electrons and become negative ions

  11. Molecular Compound • Nonmetals with nonmetals • Nonmetal oxides (CO2 or SO2) are acidic • The more nonmetallic= more acidic the oxide • Nonmetal oxide + H2O  acid [7.14] No dissociation (molecular) • Nonmetal oxide + base  salt + H2O [7.16]

  12. Metalloids • Characteristics of both metals and nonmetals. • Shiny, brittle • All solids • Semiconductors • KNOW THEM!!

  13. Overall Reactivity • The most reactive metals are the largest since they are the best electron givers. • The most reactive nonmetals are the smallest ones, the best electron takers.

  14. Overall Reactivity

  15. Homework • 7.54 through 7.64 on page 294 • EVENS only • Exclude part (a) of 7.56 • Exclude part (c) of 7.62 • Exclude part (d) of 7.64

  16. Group Trends Active Metals

  17. Group Trends: Alkali Metals • ns1 • Very reactive • Exist in nature only as compounds • Soft metallic solids • Na and K most abundant in Earth’s crust and biological systems • Physical properties: Table 7.4 on p. 281

  18. Alkali Metals React with… • Hydrogen to form hydrides [7.17] • Sulfur to form sulfides [7.18] • H2O to form metal hydroxide and H2 [7.19] • Oxygen • Li forms metal oxide [7.20] • Na forms metal peroxide [7.21] • K, Rb, and Cs form superoxides [7.22]

  19. The Alkaline Earth Metals • ns2 • Solids • Harder and more dense than alkali • Table 7.5 on p. 285 • Less reactive than alkali • Be and Mg are the least reactive

  20. Alkaline Earth Metals Reactivity • Be does not react with water or steam • Mg does not react with water, reacts with steam • Mg(s) + H2O (g)  MgO(s) +H2 (g) [7.23] • All others react with water to form metal hydroxides and H2 [7.24]

  21. The Alkaline Earth Metals • Heavier alkaline earth ions give off characteristic colors when heated • Ca = brick red • Sr = crimson red • Ba = green

  22. The Alkaline Earth Metals • Mg and Ca essential to growth and maintenance of the human body • 99% of Ca in body is in skeletal system

  23. Group Trends Selected Nonmetals

  24. Hydrogen 1s1 • Nonmetallic element in a class by itself- metallic inside the stars & Jovian planets • Most abundant element in the universe • Forms explosive mixtures with oxygen/halogens • Reacts with metals to form hydrides [7.17] • Loses it’s e- in H2O to form H+ ions

  25. Chalcogens, ns2 np4 • O, S, and Se are nonmetallic • Te is a metalloid • Po is a radioactive, rare metal • Two allotropes of O (O2 and O3) • O is a great oxidizer • S has many allotropes • S8 is the most common • S reacts with almost every metal to form sulfides

  26. Halogens, ns2,np5 • Nonmetals • Salt formers • At is rare and radioactive • All very reactive; not found in free form. • Cl has the most industrial use • Reactivity: F2 > Cl2 > Br2 > I2

  27. Noble Gases, ns2,np6 . • Each of these elements has a full octet • Used to be the inert gases • They are all unreactive • Except XeF2, XeF4, XeF6 (Bartlett, 1962) • Recently  KrF2; HArF (stable at low temp) • He is commercially available-very expensive • Ar is more common-less than 1% of the air

  28. Homework • 7.68-7.78 on page 295 • EVENS only • Not 7.68 b, c • Not 7.78 a

  29. Balanced Reactions • 7.9 • 7.12 • 7.14* • 7.16* • 7.17 (true for any metal) • 7.18 • 7.19 • 7.20 • 7.21 • 7.22 • 7.23 • 7.24 *Limited to any from the book, homework, or discussed in class

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