3.1 Classification of Matter. Copyright 2009 by Pearson Education, Inc.

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1 Chapter 3 Atoms and Elements 3.1 Classification of Matter Copyright 2009 by Pearson Education, Inc. 1

2 Matter Matter is the stuff that makes up all things. Copyright 2009 by Pearson Education, Inc. 2

3 Pure Substances A pure substance is classified as matter with a specific composition. an element when composed of one type of atom. a compound when composed of two or more elements combined in a definite ratio. 3

4 Elements Elements are pure substances that contains atoms of only one type. Copper, Cu Lead, Pb Aluminum, Al Copyright 2009 by Pearson Education, Inc. 4

5 Compounds Compounds contain two or more elements in a definite ratio. Salt (NaCl) Table sugar (C 12 H 22 O 11 ) Water (H 2 O) Copyright 2009 by Pearson Education, Inc. 5

6 Elements in a Compound Table salt is a compound that contains the elements sodium and chlorine. 6

7 Mixtures A mixture is a type of matter that consists of two or more substances that are physically mixed, not chemically combined. two or more substances in different proportions. substances that can be separated by physical methods. 7

8 Physical Separation of a Mixture Example: Pasta and water are separated with a strainer. Copyright 2009 by Pearson Education, Inc. 8

9 Homogeneous Mixtures In a homogeneous mixture, the composition is uniform throughout. the different parts of the mixture are not visible. Copyright 2009 by Pearson Education, Inc. 9

10 Heterogeneous Mixtures In a heterogeneous mixture, the composition of substances is not uniform. the composition varies from one part of the mixture to another. the different parts of the mixture are visible. Copyright 2009 by Pearson Education, Inc. 10

11 Classification of Matter 11

12 Learning Check Identify each of the following as a pure substance or a mixture. A. pasta and tomato sauce B. aluminum foil C. helium D. air 12

13 Solution Identify each of the following as a pure substance or a mixture. A. pasta and tomato sauce mixture B. aluminum foil pure substance C. helium pure substance D. air mixture 13

14 Learning Check Identify each of the following as a homogeneous or heterogeneous mixture: A. hot fudge sundae B. air C. sugar water D. peach pie 14

15 Solution Identify each of the following as a homogeneous or heterogeneous mixture: A. hot fudge sundae heterogeneous mixture B. air homogeneous mixture C. sugar water homogeneous mixture D. peach pie heterogeneous mixture 15

16 Chapter 3 Atoms and Elements 3.2 Elements and Symbols Copyright 2009 by Pearson Education, Inc. 16

17 Elements Elements are pure substances that cannot be separated into simpler substances by ordinary laboratory processes. the building blocks of matter. gold carbon aluminum 17

18 Sources of Some Element Names Some elements are named for planets, mythological figures, minerals, colors, scientists, and places. 18

19 Symbols of Elements A symbol represents the name of an element. consists of 1 or 2 letters. starts with a capital letter. 1-Letter Symbols 2-Letter Symbols C carbon Co cobalt N nitrogen Ca calcium F fluorine Al aluminum O oxygen Mg magnesium 19

20 Symbols from Latin Names Several symbols are derived from Latin names as shown below. Cu, copper (cuprum) Au, gold (aurum) Fe, iron (ferrum) Ag, silver (argentum) Copyright 2009 by Pearson Education, Inc. 20

21 Physical Properties of Elements The physical properties of an element are observed or measured without changing its identity. include the following: Shape Color Odor and taste Density Melting point Boiling point 21

22 Physical Properties of Elements Some physical properties of copper are: Color Red-orange Luster Very shiny Melting point 1083 C Boiling point 2567 C Conduction of electricity Excellent Conduction of heat Excellent Copyright 2009 by Pearson Education, Inc. 22

23 Learning Check Select the correct symbol for each. A. Calcium 1) C 2) Ca 3) CA B. Sulfur 1) S 2) Sl 3) Su C. Iron 1) Ir 2) FE 3) Fe 23

24 Solution Select the correct symbol for each. A. Calcium 2) Ca B. Sulfur 1) S C. Iron 3) Fe 24

25 Learning Check Select the correct name for each symbol. A. N 1) neon 2) nitrogen 3) nickel B. P 1) potassium 2) phlogiston 3) phosphorus C. Ag 1) silver 2) agean 3) gold 25

26 Solution Select the correct name for each: A. N 2) nitrogen B. P 3) phosphorus C. Ag 1) silver 26

27 Chapter 3 Atoms and Elements 3.3 The Periodic Table Copyright 2009 by Pearson Education, Inc. 27

28 Groups and Periods On the periodic table, elements are arranged according to similar properties. groups contain elements with similar properties in vertical columns. periods are horizontal rows of elements. 28

29 Groups and Periods Copyright 2009 by Pearson Education, Inc. 29

30 Periodic Table 30

31 Group Numbers Group Numbers use the letter A for the representative elements (1A to 8A) and the letter B for the transition elements. also use numbers 1-18 to the columns from left to right. 31

32 Names of Some Representative Elements 32

33 Alkali Metals Group 1A (1), the alkali metals, includes lithium, sodium, and potassium. Copyright 2009 by Pearson Education, Inc. 33

34 Halogens Group 7A (17), the halogens, includes chlorine, bromine, and iodine. Copyright 2009 by Pearson Education, Inc. 34

35 Learning Check Identify the element described by the following: A. Group 7A (17), Period 4 1) Br 2) Cl 3) Mn B. Group 2A (2), Period 3 1) beryllium 2) boron 3) magnesium C. Group 5A (15), Period 2 1) phosphorus 2) arsenic 3) nitrogen 35

36 Solution A. Group 7A (17), Period 4 1) Br B. Group 2A (2), Period 3 3) magnesium C. Group 5A (15), Period 2 3) nitrogen 36

37 Metals, Nonmetals, and Metalloids The heavy zigzag line separates metals and nonmetals. Metals are located to the left. Nonmetals are located to the right. Metalloids are located along the heavy zigzag line between the metals and nonmetals. 37

38 Metals, Nonmetals, and Metalloids on the Periodic Table 38

39 Properties of Metals, Nonmetals, and Metalloids Metals are shiny and ductile. are good conductors of heat and electricity. Nonmetals are dull, brittle, and poor conductors. are good insulators. Metalloids are better conductors than nonmetals, but not as good as metals. are used as semiconductors and insulators. 39

40 Comparing a Metal, Metalloid, and Nonmetal 40

41 Learning Check Identify each of the following elements as 1) metal, 2) nonmetal, or 3) metalloid. A. sodium B. chlorine C. silicon D. iron E. carbon 41

42 Solution Identify each of the following elements as 1) metal, 2) nonmetal, or 3) metalloid. A. sodium 1 metal B. chlorine 2 nonmetal C. silicon 3 metalloid D. iron 1 metal E. carbon 2 nonmetal 42

43 Learning Check Match the elements to the description. A. Metals in Group 4A (14) 1) Sn, Pb 2) C, Si 3) C, Si, Ge, Sn B. Nonmetals in Group 5A (15) 1) As, Sb, Bi 2) N, P 3) N, P, As, Sb C. Metalloids in Group 4A (14) 1) C, Si, Ge, 2) Si, Ge 3) Si, Ge, Sn, Pb 43

44 Solution Match the elements to the description. A. Metals in Group 4A (14) 1) Sn, Pb B. Nonmetals in Group 5A (15) 2) N, P C. Metalloids in Group 4A (14) 2) Si, Ge 44

45 Chapter 3 Atoms and Elements 3.4 The Atom Copyright 2009 by Pearson Education, Inc. 45

46 Dalton s Atomic Theory In Dalton s atomic theory, atoms are tiny particles of matter. of an element are similar and different from other elements. of two or more different elements combine to form compounds. are rearranged to form new combinations in a chemical reaction. 46

47 Subatomic Particles Atoms contain subatomic particles. Protons have a positive (+) charge. Electrons have a negative (-) charge. Neutrons are neutral. Like charges repel and unlike charges attract. 47

48 Rutherford s Gold Foil Experiment In Rutherford s gold foil experiment, positively charged particles were aimed at atoms of gold. mostly went straight through the atoms. were deflected only occasionally. Conclusion: There must be a small, dense, positively charged nucleus in the atom that deflects positive particles that come close. 48

49 Rutherford s Gold Foil Experiment Copyright 2009 by Pearson Education, Inc. 49

50 Structure of the Atom An atom consists of a nucleus that contains protons and neutrons. of electrons in a large, empty space around the nucleus. Copyright 2009 by Pearson Education, Inc. 50

51 Atomic Mass Scale On the atomic mass scale, 1 atomic mass unit (amu) has a mass equal to 1/12 of the mass of the carbon-12 atom. a proton has a mass of about 1 (1.007) amu. a neutron has a mass of about 1 (1.008) amu. an electron has a very small mass, amu. 51

52 Particles in the Atom 52

53 Learning Check Identify each statement as describing a 1) proton, 2) neutron, or 3) electron. A. found outside the nucleus B. has a positive charge C. is neutral D. found in the nucleus 53

54 Solution Identify each statement as describing a 1) proton, 2) neutron, or 3) electron. A. 3 found outside the nucleus B. 1 has a positive charge C. 2 is neutral D. 1, 2 found in the nucleus 54

55 Chapter 3 Atoms and Elements 3.5 Atomic Number and Mass Number Copyright 2009 by Pearson Education, Inc. 55

56 Atomic Number The atomic number is specific for each element. is the same for all atoms of an element. is equal to the number of protons in an atom. appears above the symbol of an element. Atomic Number Symbol 11 Na 56

57 Atomic Number and Protons Examples of atomic number and number of protons: Hydrogen has atomic number 1; every H atom has one proton. Carbon has atomic number 6; every C atom has six protons. Copper has atomic number 29; every Cu atom has 29 protons. Gold has atomic number 79; every Au atom has 79 protons. 57

58 Learning Check State the number of protons in each. A. A nitrogen atom 1) 5 protons 2) 7 protons 3) 14 protons B. A sulfur atom 1) 32 protons 2) 16 protons 3) 6 protons C. A barium atom 1) 137 protons 2) 81 protons 3) 56 protons 58

59 Solution State the number of protons in each. A. A nitrogen atom 2) atomic number 7; 7 protons B. A sulfur atom 2) atomic number 16; 16 protons C. A barium atom 3) atomic number 56; 56 protons 59

60 Electrons in An Atom An atom of an element is electrically neutral; the net charge of an atom is zero. has an equal number of protons and electrons. number of protons = number of electrons Aluminum has 13 protons and 13 electrons. The net (overall) charge is zero. 13 protons (13+) + 13 electrons (13 -) = 0 60

61 Mass Number The mass number represents the number of particles in the nucleus. is equal to the number of protons + the number of neutrons. 61

62 Atomic Models 62

63 Study Tip: Protons and Neutrons Number of protons = Atomic number Number of protons + neutrons = Mass number Number of neutrons = mass number atomic number (protons) Note: Mass number is given for specific isotopes only. 63

64 Learning Check An atom of zinc has a mass number of 65. A. How many protons are in this zinc atom? 1) 30 2) 35 3) 65 B. How many neutrons are in the zinc atom? 1) 30 2) 35 3) 65 C. What is the mass number of a zinc atom that has 37 neutrons? 1) 37 2) 65 3) 67 64

65 Solution An atom of zinc has a mass number of 65. A. How many protons are in this zinc atom? 1) 30 (atomic number 30) B. How many neutrons are in the zinc atom? 2) 35 (65 30 = 35) C. What is the mass number of a zinc atom that has 37 neutrons? 3) 67 ( = 67) 65

66 Learning Check An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is 1) 14 2) 16 3) 34 C. The element is 1) Si 2) Ca 3) Se 66

67 Solution An atom has 14 protons and 20 neutrons. A. It has atomic number 1) 14 B. It has a mass number of 3) 34 ( = 34) C. The element is 1) Si (Atomic number 14) 67

68 Chapter 3 Atoms and Elements 3.6 Isotopes and Atomic Mass 24 Mg 25 Mg 26 Mg Copyright 2009 by Pearson Education, Inc. 68

69 Isotopes Isotopes are atoms of the same element that have different mass numbers. have the same number of protons, but different numbers of neutrons. 69

70 Atomic Symbol An atomic symbol represents a particular atom of an element. gives the mass number in the upper left corner and the atomic number in the lower left corner. Example: An atom of sodium with atomic number 11 and a mass number 23 has the following atomic symbol: mass number 23 Na atomic number 11 70

71 Information from Atomic Symbols The atomic symbol for a specific atom of an element gives the number of protons (p + ), number of neutrons (n), and number of electrons (e - ). 71

72 Information from Atomic Symbols Examples of number of subatomic particles for atoms Atomic symbol O P Zn p + 15 p + 30 p + 8 n 16 n 35 n 8 e - 15 e - 30 e - 72

73 Learning Check Naturally occurring carbon consists of three isotopes: 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of the following: 12 C 13 C 14 C protons neutrons electrons 73

74 Solution 12 C 13 C 14 C protons 6 p + 6 p + 6 p + neutrons 6 n 7 n 8 n electrons 6 e - 6 e - 6 e - 74

75 Learning Check Write the atomic symbols for atoms with the following subatomic particles: A. 8 p +, 8 n, 8 e - B. 17p +, 20n, 17e - C. 47p +, 60 n, 47 e - 75

76 Solution A. 8 p +, 8 n, 8 e - 16 O 8 B. 17p +, 20 n, 17e - 37 Cl 17 C. 47p +, 60 n, 47 e Ag 47 76

77 Learning Check 1. Which of the pairs are isotopes of the same element? 2. In which of the pairs do both atoms have 8 neutrons? A. 15 X 15 X 8 7 B. 12 X 14 X 6 6 C. 15 X 16 X

78 Solution B. 12 X 14 X 6 6 The atomic symbols in B. represent isotopes of carbon with 6 protons each, but one has 6 neutrons and the other has 8. C. 15 X 16 X 7 8 These isotopes of nitrogen and oxygen have 8 neutrons. 78

79 Isotopes of Magnesium 79

80 Isotopes of Magnesium 80

81 Isotopes of Sulfur A sample of naturally occurring sulfur contains several isotopes with the following abundances Isotope % abundance 32 S S S S S, 33 S, 34 S, 36 S Copyright 2009 by Pearson Education, Inc. 81

82 Atomic Mass The atomic mass of an element is listed below the symbol of each element on the periodic table. gives the mass of an average atom of each element compared to 12 C. Na is not the same as the mass number. 82

83 Isotopes of Some Elements and Their Atomic Mass Most elements have two or more isotopes that contribute to the atomic mass of that element. 83

84 Atomic Mass for Cl The atomic mass of chlorine is due to all the Cl isotopes. not a whole number. the average of two isotopes: 35 Cl and 37 Cl. 84

85 Learning Check Using the periodic table, specify the atomic mass of each element. A. calcium B. aluminum C. lead D. barium E. iron 85

86 Solution Using the periodic table, specify the atomic mass of each element: A. calcium amu B. aluminum amu C. lead amu D. barium amu E. iron amu 86

87 Calculating Atomic Mass The calculation for atomic mass requires the percent(%) abundance of each isotope. atomic mass of each isotope of that element. sum of the weighted averages. mass of isotope(1)x (%) + mass of isotope(2) x (%)

88 Calculating Atomic Mass for Cl 35 Cl has atomic mass amu (75.76%) and 37 C has atomic mass amu (24.24%). Use atomic mass and percent of each isotope to calculate the contribution of each isotope to the weighted average x = amu x = amu 100 Sum is atomic mass of Cl amu 88

89 Calculating Atomic Mass Mg Isotope Mass Abundance 24 Mg = amu x 78.70/100 = amu 25 Mg = amu x 10.13/100 = amu 26 Mg = amu x 11.17/100 = amu Atomic mass (average mass) Mg = amu 89

90 Atomic Mass of Magnesium The atomic mass of Mg is due to all the Mg isotopes. is a weighted average. is not a whole number. 90

91 Learning Check Gallium is an element found in lasers used in compact disc players. In a sample of gallium, there is 60.10% of 69 Ga (atomic mass ) atoms and 39.90% of 71 Ga (atomic mass ) atoms. What is the atomic mass of gallium? 91

92 Solution 69 Ga amu x = amu (from 69 Ga) Ga amu x = amu (from 71 Ga) 100 Atomic mass Ga = amu 31 Ga

93 Chapter 3 Atoms and Elements 3.7 Electron Energy Levels Copyright 2009 by Pearson Education, Inc. 93

94 Energy Levels Energy levels are assigned numbers n = 1, 2, 3, 4, and so on. increase in energy as the value of n increases. are like the rungs of a ladder with the lower energy levels nearer the nucleus. 94

95 Energy Levels Energy levels have a maximum number of electrons equal to 2n 2. Energy level Maximum number of electrons n = 1 2(1) 2 = 2(1) = 2 n = 2 2(2) 2 = 2(4) = 8 n = 3 2(3) 2 = 2(9) = 18 95

96 Orbitals An orbital is a three-dimensional space around a nucleus, where an electron is most likely to be found. has a shape that represents electron density (not a path the electron follows). can hold up to 2 electrons. 96

97 Orbitals An s orbital has a spherical shape around the nucleus. is found in each energy level. A p orbital has a two-lobed shape. is one of three p orbitals in each energy level from n = 2. 97

98 Orbitals 98

99 Electron Level Arrangement In the electron level arrangement for the first 18 elements electrons are placed in energy levels (1, 2, 3, etc.), beginning with the lowest energy level there is a maximum number in each energy level. Energy level Number of electrons 1 2 (up to He) 2 8 (up to Ne) 3 8 (up to Ar) 4 2 (up to Ca) 99

100 Learning Check Write the electron level arrangement for each: 1. N 2. Cl 3. K 100

101 Solution Write the electron level arrangement for each: 1. N 2, 5 2. Cl 2, 8, 7 3. K 2, 8, 8, 1 101

102 Learning Check Identify the element with each electron level arrangement: 1. 2, , 8, , 7 102

103 Solution Identify the element with each electron level arrangement: 1. Be 2, 2 2. Al 2, 8, 3 3. F 2, 7 103

104 Chapter 3 Atoms and Elements 3.8 Periodic Trends Copyright 2009 by Pearson Education, Inc. 104

105 Valence Electrons The valence electrons determine the chemical properties of the elements. are the electrons in the highest energy level. are related to the group number of the element. Example: Phosphorus has 5 valence electrons. P in Group 5A(15) 2, 8, 5 5 valence electrons 105

106 Groups and Valence Electrons All the elements in a group have the same number of valence electrons. Example: Elements in group 2A (2) have two (2) valence electrons. Be 2, 2 Mg 2, 8, 2 Ca 2, 8, 8, 2 Sr 2, 8, 18, 8, 2 106

107 Periodic Table and Valence Electrons Representative Elements Group Numbers H He 1 2 Li Be B C N O F Ne 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8 Na Mg Al Si P S Cl Ar 2,8,1 2,8,2 2,8,3 2,8,4 2,8,5 2,8,6 2,8,7 2,8,8 107

108 Learning Check State the number of valence electrons for each. A. O 1) 4 2) 6 3) 8 B. Al 1) 13 2) 3 3) 1 C. Cl 1) 2 2) 5 3) 7 108

109 Solution State the number of valence electrons for each. A. O 2) 6 B. Al 2) 3 C. Cl 3) 7 109

110 Learning Check State the number of valence electrons for each. A. calcium 1) 1 2) 2 3) 3 B. group 6A (16) 1) 2 2) 4 3) 6 C. tin 1) 2 2) 4 3)

111 Solution State the number of valence electrons for each. A. calcium 2) 2 B. group 6A (16) 3) 6 C. tin 2) 4 111

112 Learning Check For the element with the following electron arrangement: 1) State the number of valence electrons. 2) Identify the element. A. 2, 8, 5 B. 2, 8, 8, 2 C. 2, 7 112

113 Solution For the element with the following electron arrangement 1) State the number of valence electrons 2) Identify the element. A. 2, 8, 5 1) 5 2) phosphorus B. 2, 8, 8, 2 1) 2 2) calcium C. 2, 7 1) 7 2) fluorine 113

114 Electron-Dot Symbols An electron-dot symbol shows the valence electrons around the symbol of the element. for Mg has 2 valence electrons as single dots on the sides of the symbol Mg... Mg or Mg or Mg or Mg 114

115 Writing Electron-Dot Symbols Electron-dot symbols for groups 1A (1) to 4A (14) use single dots. Na Mg Al C groups 5A (15) to 7A (17) use pairs and single dots. P : O 115

116 Groups and Electron-Dot Symbols In a group, all the electron-dot symbols have the same number of valence electrons (dots). Example: Atoms of elements in Group 2A (2) each have 2 valence electrons. Be Mg Ca Sr Ba 116

117 Learning Check. A. X is the electron-dot symbol for 1) Na 2) K 3) Al.. B.. X.. is the electron-dot symbol of 1) B 2) N 3) P 117

118 Solution. A. X is the electron-dot symbol for 1) Na 2) K.. B.. X.. is the electron-dot symbol of 2) N 3) P 118

119 Atomic Size Atomic size is described using the atomic radius; the distance from the nucleus to the valence electrons. 119

120 Atomic Radius Within A Group Atomic radius increases going down each group of representative elements. 120

121 Atomic Radius Across a Period Going across a period from left to right, an increase in the number of protons increases attraction for valence electrons. atomic radius decreases. Copyright 2009 by Pearson Education, Inc. 121

122 Learning Check Select the element in each pair with the larger atomic radius. A. Li or K B. K or Br C. P or Cl 122

123 Solution Select the element in each pair with the larger atomic radius. A. K B. K C. P 123

124 Ionization Energy Ionization energy is the energy it takes to remove a valence electron. Na(g) + Energy (ionization) -> Na + (g) + e - 124

125 Ionization Energy In a Group Going up a group of representative elements, the distance decreases between nucleus and valence electrons. the ionization energy increases. 125

126 Ionization Energy Metals have lower ionization energies. Nonmetals have higher ionization energies. Copyright 2009 by Pearson Education, Inc. 126

127 Learning Check Select the element in each pair with the higher ionization energy. A. Li or K B. K or Br C. P or Cl 127

128 Solution Select the element in each pair with the higher ionization energy. A. Li B. Br C. Cl 128