Properties of Atoms and the Periodic Table

Transcription

1 Physical Science Chapter 17 Properties of Atoms and the Periodic Table Videos attached to this document will not work online. DefinitionofAtoms

2 Unit 4 The Nature of Matter CLE: Describe the structure and arrangement of atomic particles.

3 17:1 Structure of the Atom Scientists have developed their own shorthand for dealing with long, complicated names. Chemical symbols consist of one capital letter or a capital letter plus one or two smaller letters.

4 17:1 Scientific Shorthand Elements are abbreviated in scientific shorthand first letter or two of element s name.

5 17:1 The Scientific Shorthand For some elements, the symbol is the first letter of the element's name. For other elements, the symbol is the first letter of the name plus another letter from its name. Because scientists worldwide use this system, everyone understands what the symbols mean. 5

6 17:1 Structure of the Atom Atomic Compounds Aluminum Al Calcium Ca Carbon.C Chlorine Cl Copper.Cu Gold Au Helium He Hydrogen..H Iodine I Iron Fe Fluorine F Magnesium..Mg Memorize These. There will be quizzes often over the element and their symbols. STUDY. 6

7 17:1 Structure of the Atom Atomic Compounds Mercury.Hg Nitrogen.N Oxygen O Potassium.K Silver Ag Sodium.Na Lead..Pb Radium Ra Chromium...Cr Zinc Zn Neon Ne Platinum..Pt Sulfur S Memorize These. There will be quizzes often over the element and their symbols. STUDY. Write-off follow. 7

8 17.1 Irregular Chemical Symbols The chemical symbols for the following elements are not abbreviations of their English names. Copper is Cu, for cuprum. Gold is Au for aurum. Iron is Fe for ferrum. Lead is Pb for plumbum. Tin is Sn for stannum. Mercury is Hg for hydrargyrum. Silver is Ag for argentum. Sodium is Na for natrium. Potassium is K for kalium. Antimony is Sb for stibium and Tungsten is W for wolfram. 8

9 17:1 Structure of the Atom 1. An element is matter that is composed of one type of atom. An atom is the smallest piece of matter that still retains the properties of the element. 2. Atoms are composed of particles called protons, neutrons, and electrons. Play Video 9

10 17:1 Atomic Components 3. Protons and neutrons are found in a small positively charged center of the atom called the nucleus that is surrounded by a cloud containing electrons. 4. Protons are particles with an electrical charge of

11 17.1 Quarks Even Smaller Particles 5. Protons and neutrons are made up of smaller particles called quarks. So far, scientists have confirmed the existence of six uniquely different quarks. 11

12 17:1 Atomic Components 6. Neutrons are neutral particles that do not have an electrical charge. 7. Electrons are particles with an electrical charge of 1. LookingInside

13 17.1 Quarks Even Smaller Particles Scientists theorize that protons are made of three quarks held together with the strong nuclear force. Another arrangement of three quarks produces a neutron. 13

14 B. Quarks are Smaller Particles. 1. Protons and neutrons are made up of smaller particles called quarks. 2. Quarks are studied by colliding accelerated charged particles with protons, which leave tracks in a bubble chamber. 3. Six quarks are known to exist; the sixth is called the top quark. 14

15 Structure of the Atom 17:1 Models Tools for Scientists Scientists and engineers use models to represent things that are difficult to visualize or picture in your mind. Scaled-down models allow you to see either something too large to see all at once, or something that has not been built yet. Scaled-up models are often used to visualize things that are too small to see. 15

16 17.1 Models Tools for Scientists To study the atom, scientists have developed scaled-up models that they can use to visualize how the atom is constructed. Scientists use scaled-up models to represent atoms. 16

17 17.1 The Changing Atomic Model In the 1800s, John Dalton, an English scientist, was able to offer proof that atoms exist. Democritus proposed that elements consisted of tiny, solid particles that could not be subdivided. Another famous Greek philosopher, Aristotle, disputed Democritus's theory and proposed that matter was uniform throughout and was not composed of smaller particles. 17

18 C. The Changing Atomic Model In the 1800s, John Dalton, an English scientist, was able to offer proof that atoms exist. 1. Dalton's and other scientists used a solid sphere as an early model of the atom. The model has changed somewhat over time. 18

19 17.1 The Electron Cloud Model 2. By 1926, scientists had developed the electron cloud model of the atom that is in use today. a. An electron cloud is the area around the nucleus of an atom where its electrons are most likely found. b. The electron cloud model shows electrons traveling around in specific energy levels around a nucleus of protons and neutrons. StructureofAtoms2.42

20 Section Check Question 1 Which is the smallest piece of matter that still retains the property of the element? A. atom B. quark C. neutron D. proton Answer The answer is A. An atom is the smallest piece of matter that still retains the property of the element. 20

21 Question 2 What particles are found in the nucleus of an atom? A. protons and electrons B. protons and neutrons C. neutrons and electrons D. quarks and electrons 21

22 Answer The answer is B. Electrons are located in an electron cloud surrounding the nucleus of the atom. 22

23 Question 3 What is the name of the small particles that make up protons and neutrons? Answer Protons and neutrons are made of smaller particles called quarks. 23

24 Drawing Reminder Figure 1. Pg. 507 Plain, appropriately sized paper Pasted to flip Must have a title (Not Figure 1) Colored, if colored in book Do not use back of paper Include labels Write the entire caption minus any questions in the caption.

25 17.2 Atomic Mass The nucleus contains most of the mass of the atom because protons and neutrons are far more massive than electrons. The mass of a proton is about the same as that of a neutron. Just How Small is the Atom? 24

26 17.2 Atomic Mass The mass of each proton and neutron is approximately 1,836 times greater than the mass of the electron. 25

27 17.2 Atomic Mass 1. The unit of measurement used for atomic particles is the atomic mass unit (amu). 2. The mass of a proton or a neutron is almost equal to 1 amu. 3. The atomic mass unit is defined as one-twelfth the mass of a carbon atom containing six protons and six neutrons. 26

28 B. Protons Identify the Element The number of protons tells you what type of atom you have and vice versa. For example, every carbon atom has six protons. Also, all atoms with six protons are carbon atoms. 1. The number of protons in an atom is equal to a number called the atomic number. 27

29 17.2 Mass Number 2. The mass number of an atom is the sum of protons and neutrons in the nucleus of an atom. 28

30 17.2 Mass Number If you know the mass number and the atomic number of an atom, you can calculate the number of neutrons. number of neutrons = mass number atomic number Atomic Mass2.09 Atomic Number

31 Summary Handout Math Problems. Paste in as demonstrated by teacher. Learn These Facts. Write these in your notebook now. Atomic Number=Number of Protons Number of Electrons = Number of Protons Neutrons = Mass Number Number of Protons Neutrons + Protons = Mass Number Do the Practice Problems Now. 30

32 Element Symbol Atomic # Atomic Mass # P #N #E Helium He Magnesium Mg Zinc Zn Bromine Br Aluminum Al Uranium U Sodium Na Krypton Kr Calcium Ca Silver Ag

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34 Isotopes Not all the atoms of an element have the same number of neutrons. C. Atoms of the same element that have different numbers of neutrons are called isotopes. 33

35 17.2 Isotopes Models of two isotopes of boron are shown. Because the numbers of neutrons in the isotopes are different, the mass numbers are also different. You use the name of the element followed by the mass number of the isotope to identify each isotope: boron-10 and boron

36 Isotopes 1. Different isotopes have different properties. 2. Number of neutrons is equal to mass number minus atomic number. 3. Name of element followed by mass number identifies the isotope. 4. Average atomic mass is the weightedaverage mass of an element s isotopes. 5. Average atomic mass is closest to its most abundant isotope. 35

37 Calculation Atomic Mass To calculate the atomic mass of a compound, add the atomic mass of each atom. Example FeBr 3 Fe = x 1 =55.85 Br = x 3 = = amu 36

38 17.2 Isotopes Isotopes4.18 The average atomic mass of an element is the weighted-average mass of the mixture of its isotopes. For example, four out of five atoms of boron are boron-11, and one out of five is boron-10. To find the weighted-average or the average atomic mass of boron, you would solve the following equation: 37

39 C 4 H Calculation Atomic Mass Calculate the atomic mass of these compounds in your notebook. Title it Mass 1. Ca(NO 2 ) 2 H 2 SO 4 H 2 O K 2 CO 3 (NH 4 ) 3 PO 4 CO 2 (C 2 H 9 ) 2 Pb Ag 2 O NaCl

40 Calculation Atomic Mass Calculate the atomic mass of these compounds in your notebook. Title it Mass Ca(NO 2 ) 2 H 2 SO 4 H 2 O K 2 CO (NH 4 ) 3 PO 4 CO 2 (C 2 H 9 ) 2 Pb Ag 2 O NaCl C 4 H

41 18:2 Let s Review Calculate the average atomic mass of these compounds. Ca x 1 = N x 4 = Ca(NO2)4 4. NaCl O x 8 = H x 4= S x 2 = O x 8 = (H2SO4) 5. BaCl Na x 1 = Cl x 1 = Ba x 1= Cl x H x 2 = O x 1 = H2O C6H12O6 C x 6 = H x 12 = O x 6 =

42 Section Check Question 1 How is the atomic number of an element determined? Answer The atomic number of an element is equal to the number of protons in an atom of that element. 42

43 Question 2 The element helium has a mass number of 4 and atomic number of 2. How many neutrons are in the nucleus of a helium atom? Answer Recall that the atomic number is equal to the number of protons in the nucleus. Since the mass number is 4 and the atomic number is 2, there must be 2 neutrons in the nucleus of a helium atom. 43

44 Question 3 How much of the mass of an atom is contained in an electron? Answer The electron s mass is so small that it is considered negligible when finding the mass of an atom. 44

45 17.3 The Periodic Table Organizing the Elements A. The Periodic Table. (Periodic means "repeated in a pattern." ) 1. In the late 1800s, Dmitri Mendeleev, a Russian chemist, devised the first periodic table based on atomic masses. 45

46 17.3 The Periodic Table Organizing the Elements Because the pattern repeated, it was considered to be periodic. Today, this arrangement is called a periodic table of elements. 2. In the periodic table, the elements are arranged by increasing atomic number and by changes in physical and chemical properties. 46

47 17.3 The Periodic Table Mendeleev s Predictions Mendeleev had to leave blank spaces in his periodic table to keep the elements properly lined up according to their chemical properties. Mendeleev looked at the properties and atomic masses of the elements surrounding these blank spaces. His periodic table was arranged based on atomic mass. 47

48 17.3 The Periodic Table Mendeleev s Predictions From this information, he was able to predict the properties and the mass numbers of new elements that had not yet been discovered. 48

49 17.3 The Periodic Table Mendeleev s Predictions This table shows Mendeleev's predicted properties for germanium, which he called ekasilicon. His predictions proved to be accurate. 49

50 17.3 Improving the Periodic Table On Mendeleev's table, the atomic mass gradually increased from left to right. If you look at the modern periodic table, you will see several examples, such as cobalt and nickel, where the mass decreases from left to right. 50

51 17.3 Improving the Periodic Table 3. In 1913, the work of Henry G.J. Moseley, a young English scientist, made an arrangement of elements based on their increasing atomic numbers instead of an arrangement based on atomic masses. 4. The current periodic table uses Moseley's arrangement of the elements. 51

52 17.3 Electron Cloud Structure In a neutral atom, the number of electrons is equal to the number of protons. Therefore, a carbon atom, with an atomic number of six, has six protons and six electrons. 52

53 17.3 Electron Cloud Structure 5. Energy levels nearer the nucleus have lower energy than those levels that are farther away. 6. Electrons fill these energy levels from the inner levels (closer to the nucleus) to the outer levels (farther from the nucleus). 53

54 17.3 Electron Cloud Structure 7. Elements that are in the same group have the same number of electrons in their outer energy level. 8. It is the number of electrons in the outer energy level that determines the chemical properties of the element. 54

55 17.3 Energy Levels For example, energy level one can contain a maximum of two electrons. Energy level 2 can contain at most eight electrons. 55

56 17.3 Energy Levels Each row in the periodic table ends when an outer energy level is filled. 56

57 17:2 Masses of Atoms Atomic Mass

58 Rows on the Table The first row has hydrogen with one electron and helium with two electrons both in energy level one. Energy level one can hold only two electrons. Therefore, helium has a full or complete outer energy level. 58

59 Rows on the Table The second row begins with lithium, which has three electrons two in energy level one and one in energy level two. Lithium is followed by beryllium with two outer electrons, boron with three, and so on until you reach neon with eight outer electrons. UsingtheModernPT

60 B. Electron Dot Diagrams Elements that are in the same group have the same number of electrons in their outer energy level. These outer electrons are so important in determining the chemical properties of an element that a special way to represent them has been developed. 60

61 Electron Dot Diagrams 1. An electron dot diagram uses the symbol of the element and dots to represent the electrons in the outer energy level. 2. Electron dot diagrams are used also to show how the electrons in the outer energy level are bonded when elements combine to form compounds.

62 Same Group Similar Properties A common property of the halogens is the ability to form compounds readily with elements in Group 1. The Group 1 element, sodium, reacts easily with the Group 17 element, chlorine. The result is the compound sodium chloride, or NaCl ordinary table salt. 62

63 Same Group Similar Properties Not all elements will combine readily with other elements. 3. The elements in Group 18 have complete outer energy levels. This special configuration makes Group 18 elements relatively unreactive. 63

64 Make Electron Dot Diagrams for These Elements in Notebook: Li Mg F S Show how these elements might combine to reach their goal of complete outer energy levels: Li F Mg S

65 Li F

66 17.3 Regions on the Periodic Table The periodic table has several regions with specific names. 1. The horizontal rows of elements on the periodic table are called periods. 2. The elements increase by one proton and one electron as you go from left to right in a period. 66

67 17.3 Improving the Periodic Table 3. The vertical columns in the periodic table are called groups, or families, and are numbered 1 through

68 17.3 Regions on the Periodic Table 4. Elements are classified as metals, nonmetals and metalloids. All of the elements on the left side of the table are metals. 68

69 17.3 Regions on the Periodic Table Those elements on the right side of the periodic table, in yellow, are classified as nonmetals. 69

70 17.3 Regions on the Periodic Table 5. The elements located on the stair-step dividing line are metalloids. 70

71 A Growing Family In 1994, scientists at the Heavy-Ion Research Laboratory in Darmstadt, Germany, discovered element 111. Element 112 was discovered at the same laboratory. Both of these elements are produced in the laboratory by joining smaller atoms into a single atom. 71

72 Elements in the Universe 1. The same elements exist throughout the universe. Elements are synthesized in laboratories all over the world. 2. Hydrogen and helium are the building blocks of other elements. 72

73 Elements in the Universe Exploding stars, or supernovas, give scientists evidence to support this theory. 3. Many scientists believe that supernovas have spread the heavier elements throughout the universe. 73

74 Section Check Question 1 How are the elements arranged in the periodic table? 74

75 Answer The elements are arranged by increasing atomic number and by changes in physical and chemical properties. 75

76 Question 2 What do the elements in a vertical column of the periodic table have in common? Answer The vertical columns in the periodic table are called groups; elements in the same group have similar properties, such as electrical conductivity. 76

77 Question 3 What do the dots in this electron dot diagram represent? 77

78 Answer The dots represent the electrons in the outer energy level. 78

79 17. Review The central core of an atom is called the. The chart showing the classifications of elements according to their properties and increasing atomic numbers is called the. nucleus periodic table. 79

80 17. Review The mass of a is about equal to the mass of a proton. neutron Elements arranged in vertical columns in the periodic table are called. groups 80

81 17. Review The region around the nucleus occupied by the electrons is called. Electron cloud The symbol for chlorine is. Cl 81

82 17. Review The maximum number of electrons in the second energy level of an atom is. Two isotopes of carbon are carbon -12 and carbon 14. These isotopes differ from one another by two. 8 neutrons 82

83 17. Review Metals are conductors of heat and electricity. good Scientists believe that naturally occurring elements are manufactured within. stars 83

84 17. Review So far, scientists have confirmed the existence of different quarks. In 1926, scientists developed the model of the atom that is used today. 6 Electron cloud 84

85 17. Review Electron are used to show how electrons in the outer energy level are bonded when elements combine to form compounds. Dot diagrams The atomic number of an element is determined by its number of. protons 85

86 17. Review According to present atomic theory, the location of an in an atom cannot be pinpointed exactly. electron Moving from left to right in a row of the periodic table, metallic properties. decrease 86

87 17. Review Each inner energy level of an atom has a maximum number of it can hold. electrons Dot diagrams are used to represent. Outer level electrons 87

88 17. Review Particles of matter that make up protons and neutrons are. quarks A chemical symbol represents the of an element. name 88

89 17. Review Horizontal rows of the periodic table are called. periods Atoms of the same element with different numbers of neutrons are called. isotopes 89

90 17. Review A particle that moves around the nucleus is a(n). electron Elements that are gases, are brittle, and are poor conductors at room temperature are. nonmetals 90

91 17. Review A is used to accelerate protons in the study of subatomic particles. tevatron A certain atom has 26 protons, 26 electrons and 30 neutrons. Its mass number is

92 17. Review Suppose that you have discovered a new element and have named it neptunite. While studying your new element, you find that it has two isotopes neptunite-220 and neptunite-250. What is the average atomic mass of your new element assuming that these two isotopes are present in equal amounts in nature? 235 amu 92

93 17. Review Assume that an element is composed of one isotope with a mass of 142 and another isotope with a mass of 145. For each atom with a mass of 142 there are three atoms with a mass of 145. What is the average atomic mass of the element?

94 The End Text Coming Next Homework Notebook Due