1. Chapter 9 The Periodic Table

2. Properties of matter are altered by any of a variety of processes For changes of state, the cause of the alteration is due to the change in the motions and separations of the molecules of the material In other processes, the changes are in the molecules themselves – rusting of iron. This is a chemical reaction

3. Chemical Reactions In a chemical reaction, the atoms of the reacting substances combine differently to form new substances A chemical reaction alters the substances involved

4. Zinc and Sulfur Chemical Reaction Figure 9-1 Tam9s6_1

5. Three Classes of Matter Elements Compounds Mixtures

6. Three Classes of Matter Elements – The simplest substances present in bulk matter. Elements cannot be changed or decomposed into other elements by chemical means. More than 100 elements are known today, most of which are solids at room temp. and atm. pressure.

7. Element Distributions Universe – 75% is composed of H and nearly all the rest is He. Earth – iron, oxygen, silicon, and magnesium make up 96% of the earth’s mass. Human Body – oxygen is the most abundant element, followed by C, H, N, Ca, and P.

9. THREE CLASSES OF MATTER Compounds – are materials consisting of two or more elements joined together.

10. THREE CLASSES OF MATTER Mixtures – Other materials can be mixtures of elements or compounds or both. A heterogeneous mixture has properties that vary from one particle to another. When the components are thoroughly mixed and the result is uniform, a homogeneous mixture, or solution exists.

11. Classification of Matter Tam9s6_2 Figure 9-2

12. How can you tell when two elements are a compound or a solution? See whether the new material can be separated into different substances by boiling or freezing. Changes of state occur at specific temperatures for elements and compounds but not for mixtures.

13. Tam9s6_3 Figure 9-3 Compound or Solution?

14. How can you tell when two elements are a compound or a solution? Compare the relative amounts of the elements in different samples of the material. The elements in a given compound are always present in exactly the same proportions by mass (Law of Definite Proportions)

15. Figure 9-4 Tam9s6_4 Law of Definite Proportions

16. Atomic Theory (John Dalton 1766-1844) Prior to John Dalton (1766-1844), the structure of matter was largely a mystery Nobody knew what really happens when elements combine to form compounds

17. Atomic Theory (John Dalton 1766-1844) Dalton provided the explanation. proposed that all atoms of each element were the same but were different from the atoms of other elements established the relative masses of atoms of the known elements a compound has a fixed ratio of the kinds of atoms present Chemical reactions represent rearrangements of atoms, not changes in the atoms or the creation or destruction of atoms

18. Molecules Our modern picture of matter grew from Dalton’s work In the case of gases, the ultimate particles of a gaseous compound are its molecules, which are made up of atoms of the elements in the compound Molecules of a compound have fixed composition (Law of Definite Proportions)

19. Fixed Ratios of Molecules in Common Molecules Figure 9-5 Tam9s6_5

21. Chemical Formulas Two or more atoms linked into a molecule are represented by writing the symbols for their elements side by side These expressions are called chemical formulas Water is H 2 0 carbon monoxide is CO

22. Not all Compounds Consist of Molecules Elements in liquid and solid form are usually assemblies of individual atoms Some liquid and solid compounds are also assemblies of individual molecules Others are assemblies of IONS NaCl (table salt), a compound of sodium and chlorine, consist of sodium and chlorine IONS in a definite proportion rather than neutral atoms or molecules; NaCl is still a compound, just like water, even though it is not composed of separate molecules

23. Not all Compounds Consist of Molecules Figure 9-6 Tam9s6_6 Sodium Ion Chlorine Ion

24. Periodic Law The Periodic Law was first formulated in detail by Dmitri Mendeleev (1834-1907), a Russian chemist The element mendelevium (atomic number 101) was named in his honor. The Periodic Law states that if the elements are listed in order of atomic number, elements with similar chemical and physical properties appear at regular intervals. Such similar elements form groups.

25. Metals All metals, except Hg, are solid at room temperature Metals outnumber nonmetals 5:1 Metallic luster - one physical property that distinguishes metals from nonmetals

26. Metals Opaque Good conductors of heat and electricity Can be shaped by bending or hammering

27. Nonmetals Nonmetals can be solid, liquid, or gaseous at room temperature Solid nonmetals do not show metallic luster Nearly all are transparent in thin sheets

28. Nonmetals Solid nonmetals are brittle and break when force is applied Nonmetals are insulators

29. Metals vs Non Metals http://hyperphysics.phy- astr.gsu.edu/hbase/pertab/metal.html#c1

30. Chemical Activity Metals and nonmetals differ in their chemical properties An active metal or active nonmetal means that they readily combine to form compounds

31. Chemical Activity The more active an element is, the more stable its compounds An inactive element tends not to react chemically

32. Determining Relative Activities The relative activities of different elements can be established by measuring the amounts of heat given off in similar chemical reactions

33. Determining Relative Activities Or, you can start with similar compounds and see how easily they can be separated into their component elements

34. Tam9s6_8 Figure 9-8 Chemical Activities

35. Families of Elements Some elements resemble one another so much that they are grouped together in the Periodic Table of the Elements

36. Halogens Active nonmetals F is the most active element of all Produce bad odors and brilliant colors

37. Halogens Compounds contain two atoms at ordinary temps (F 2, Cl 2, Br 2 ) All react with H to form HF, HCl, HBr, etc.

38. Alkali Metals Active metals soft, low melting points lose their luster quickly in air

39. Alkali Metals liberate H from water and dilute acid Combine with active nonmetals to form very stable compounds

40. Inert Gases Undergo almost no chemical reactions Found in small amounts in the atmosphere Some inert gases glow in various colors when excited by an electric current and are used in signs

41. Tam9s6_9 Figure 9-9 Families of Elements

42. Tam9s6_10 Figure 9-10 Transition Elements are Metals Transition Metals

43. The Periodic Table A listing of the elements according to atomic number in a series of rows such that elements with similar properties form vertical columns halogen is followed in atomic number by an inert gas and then an alkali metal

44. Groups The periodic table arranges families of similar elements in vertical columns called groups alkali metals inert gases nonmetals halogens

45. Periods The horizontal rows in the periodic table are called periods and contain elements with widely different properties

46. Periods Across each period a change occurs from active through less active metal and weakly active nonmetals to highly active nonmetals and finally to an inert gas

47. Figure 9-7 Tam9s6_7

48. TABLE 9-7 Electron Structure How an atom’s electron structure is determines its chemical behavior

49. Tam9s6_11 Figure 9-11 Electron Structures of Some Atoms

50. Types of Chemical Bonds Covalent Bond – A bond where one or more pairs of electrons are shared by the two atoms The shared electrons spend more time between the atoms than on their far sides, which produces an attractive force

51. Covalent Bonds (Con’t) In some molecules more than one pair of electrons is shared. Examples: O 2 shares 2 pair of electrons and is shown as O : : O and N 2 shares 3 pair of electrons (N : : : N)

52. Covalent Bonds (Con’t) In some covalent compounds the shared electron pairs are closer to one atom than to the other. This is referred to as a polar covalent compound. Examples include HCl shown as H : Cl. Covalent compounds that contain carbon are called organic compounds.

53. Covalent Bonding in Hydrogen Tam9s6_13 Figure 9-13

54. Ionic Bond One or more electrons from one atom shift to another atom The resulting positive and negative ions attract each other

55. Ionic Bond Often involves a metal (which has electrons to give up in its outer shell) and a nonmetal (which needs to add electrons to its outer shell)

56. Tam9s6_14 Figure 9-14 Ionic Bonding

57. Rules for Naming Compounds The ending –ide usually indicates a compound having only two elements such as NaCl and CaO. The hydroxides (OH - ) are the exception to this rule ( Ba(OH) 2 ).

58. Rules for Naming Compounds The ending –ate indicates a compound that contains oxygen and two or more other elements (Na 2 SO 4, KNO 3 )

59. Rules for Naming Compounds When the same pair of elements occurs in two or more compounds, a prefix (mono- = 1, di- = 2, tri- = 3, tetra- = 4, penta- = 5, hexa- = 6) may be used to indicate the number of one or both kinds of atom in the molecule CO is carbon monoxide CO 2 is carbon dioxide

60. Rules for Naming Compounds When one of the elements in a compound is a metal that can form different ions, the scheme mentioned in Sec. 9-14 is used In this scheme the ionic charge of the metal is given by a roman numeral (Iron(II) chloride FeCl 2 )

61. Rules for Naming Compounds The names of molecular compounds that contain H often follow tradition instead of a definite system CH 4 - methane H 2 O - water

62. page 312 for equations Chemical Equations Are the shorthand way to express the results of a chemical reaction Reactants (reacting substances) appear on the left-hand side of the chemical equation

63. page 312 for equations Chemical Equations The formula of the products appears on the right-hand side The number of atoms of each kind must be the same on both sides of the equation This is referred to as balanced

64. Tam9s6_18 Figure 9-18 Electrolysis of Water