2. Atoms, Elements, and Ions

3. The Language of Chemistry CHEMICAL ELEMENTS -CHEMICAL ELEMENTS - –pure substances that cannot be decomposed by ordinary means to other substances. Sodium Bromine Aluminum

4. Lesson 1 The Atom: From Idea to Theory Essential Question How has the theory of the atom evolved over time? Objectives To summarize Dalton’s atomic theory. To explain the laws that support Dalton’s atomic theory.

5. An atom consists of a nucleusnucleus –(of protons and neutrons) electrons in space about the nucleus.electrons in space about the nucleus. The Atom Nucleus Electron cloud

6. The Structure of An Atom

7. Copper atoms on silica surface. An atom is the smallest particle of an element that has the chemical properties of the element.An atom is the smallest particle of an element that has the chemical properties of the element. Distance across = 1.8 nanometer (1.8 x 10 -9 m)

8. History of the atom Not the history of atom, but the idea of the atom. Original idea began 1.Ancient Greece (400 B.C.) »Democritus- Greek philosopher “father of modern science” 2.India (600B.C.) 1.Hindu Nyaya philosophy Not really sure which one.

9. History of Atom Looked at beach Made of sand Cut sand - smaller sand n Smallest possible piece? n Atomos - not to be cut

10. Another Greek Aristotle - Famous natural philosopher Believer of the 4 earthly elements – Fire - Hot – Air - light – Earth - cool, heavy – Water – wet Plus one of his own »Aether – divine/heavenly bodies Blend these elements in different proportions to get all substances

11. Who Was Right? Greek society was slave based. Beneath famous to work with hands. Did not experiment. Greeks settled disagreements by argument. Aristotle was more famous, so he won. His ideas carried through middle ages. Later, Alchemists attempted to change lead to gold.

12. Who’s Next? Late 1700’s - John Dalton- from England. –Math & natural philosophy tutor- summarized results of his experiments and those of others. Dalton’s Atomic Theory Combined ideas of elements with that of atoms.

13. Dalton’s Atomic Theory 1.matter is composed, indivisible particles (atoms) 2.all atoms of a particular element are identical 3.different elements have different atoms 4.atoms combine in certain whole-number ratios 5.Chemical reactions involve the rearrangement of atoms.  No atoms are created, destroyed, or changed into atoms of any other elements.

14. Dalton’s support for his theory Law of Conservation of Mass – Mass is neither created nor destroyed during ordinary chemical reactions. Let’s look at an equation: 2H 2 + O 2 >> 2H 2 O The quantity and mass of reactants equals the quantity and mass of the products.

15. Problems with Dalton’s Atomic Theory? 1. matter is composed, indivisible particles Atoms Can Be Divided, but only in a nuclear reaction 2. all atoms of a particular element are identical Does not Account for Isotopes (atoms of the same element but a different mass due to a different number of neutrons)! 3. different elements have different atoms YES! 4. atoms combine in certain whole-number ratios YES! Called the Law of Definite Proportions 5. In a chemical reaction, atoms are merely rearranged to form new compounds; they are not created, destroyed, or changed into atoms of any other elements. Yes, except for nuclear reactions that can change atoms of one element to a different element

16. Modern Atomic Theory We know today that atoms are made of electrons, protons, neutrons. We will study that next. Even More Modern Atomic Theory Known as the Standard Model protons & neutrons are made of six different “flavors” of quarks. Electrons are made of leptons

17. Plus there’s more Fermions Baryons Neutrinos Gluons Higgs-Boson – the most fundamental particle Not to mention that EVERY particle of matter has an antimatter counterpart. But we are not studying this stuff!

18. Learning Check 1a 1.C + O 2 >> ?? According to the Law of Conservation of Mass, the correct answer for the product is: A.CO B.C 2 O C.CO 2 D.C 1/2 O

19. Learning Check 1b Which of Dalton’s statement(s) is NO longer correct today? 1.All matter is composed of atoms. 2.Atoms of any given element are identical, and are different than atoms of another element. 3.Atoms cannot be created, destroyed, or subdivided. 4.Atoms of different elements combine in whole number ratios. 5.In chemical reactions, atoms are combined, separated, or rearranged. Isotopes-atoms of an element with different # neutrons Nuclear fission – splitting an atom

20. Learning Check 1c Explain how an idea, an opinion, a theory, and a law all become connected? First, someone has an idea; then persuades others to believe, which is an opinion. Skeptical people need proof. Experiments and data provide proof which creates a theory. After many, many years of experiments trying to disprove without success, a theory becomes a law.

21. Lesson 2 Structure of the Atom Essential Question How has scientific discovery and technology supported the structure of the atom? Objectives To summarize the experiments that contributed to the structure of the atom. –Describe the structure of an atom including location of protons, electrons, and neutrons with respect to the nucleus. –Distinguish among protons, electrons, and neutrons in terms of relative mass and charge.

22. Parts of Atoms J. J. Thomson - English physicist. (1897) Made a piece of equipment called a cathode ray tube. It is a vacuum tube - all the air has been pumped out.

23. Thomson’s Experiment Voltage source +- Vacuum tube Metal Disks

24. Thomson’s Experiment Voltage source +-

25. Thomson’s Experiment Voltage source +-

26. Thomson’s Experiment Voltage source +-

27. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

28. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

29. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

30. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

31. Thomson’s Experiment By adding an electric field

32. Voltage source Thomson’s Experiment n By adding an electric field + -

33. Voltage source Thomson’s Experiment n By adding an electric field + -

34. Voltage source Thomson’s Experiment n By adding an electric field + -

35. Voltage source Thomson’s Experiment n By adding an electric field + -

36. Voltage source Thomson’s Experiment n By adding an electric field + -

37. Voltage source Thomson’s Experiment n By adding an electric field he found that the moving pieces had a negative charge + -

38. More from Thomson JJ Thomson third experiment confirmed that the negative charge was coming from very tiny particles (1000x smaller than hydrogen atom) and were not rays. He called them electrons. In 1904 Thomson proposed his model of an atom. –Original knickname - Plum Pudding Model –Today’s knickname – Blueberry Muffin model (Why?)

39. Millikan’s Experiment (1909) Millikan determined the size of the charge of an electron. He put a charge on a tiny drop of oil and measured how strong an electric field had to be in order to stop the oil drop from falling.

40. Rutherford’s experiment Ernest Rutherford -English physicist. (1911) –Believed in Thomson’s model of the atom (1904). –Wanted to see how big they are. –Used radioactivity. –Alpha particles - positively charged pieces- helium atoms minus electrons –Shot them at gold foil which can be made a few atoms thick.

41. Rutherford’s experiment When an alpha particle hits a fluorescent screen, it glows. Here’s what it looked like

42. Lead block Uranium Gold Foil Fluorescent Screen

43. He Expected The alpha particles to pass through without changing direction very much. Because…? …the positive charges were thought to be spread out evenly. Alone they were not enough to stop the alpha particles.

44. What he expected

45. Because

46. He thought the mass was evenly distributed in the atom

47. Since he thought the mass was evenly distributed in the atom

48. What he got

49. + How he explained it Atom is mostly empty. Small dense, positive piece at center. Alpha particles are deflected by it if they get close enough.

50. +

51. Density & the Atom Conclusion Since most of the particles went through, it was mostly empty space. Because the pieces turned so much, the positive pieces were heavy. Small volume, big mass, big density. This small dense positive area is the nucleus.

52. Learning Check 2a Subatomic particles Electron Proton Neutron NameSymbolCharge Relative mass Actual mass (g) e-e- p+p+ n0n0 +1 0 0.0055 1 1 9.11 x 10 -28 1.67 x 10 -24

53. Learning Check 2b ScientistDiscovery RutherfordA. Mass of electrons ThomsonB. Positive charge of nucleus MillikanC. negative charge of electrons B C A

54. More on Rutherford 1911 – he named the center of atom nucleus, meaning “little nut.” Designed a model of the atom 1920 – After further experiments Rutherford named the + charged particles in the nucleus – protons. He predicted that there was a mass of neutral charge particles in the nucleus, but did not conduct any experiments.

55. Rutherford Atom Model no neutrons yet

56. Discovery of the neutron It was known, but not understood, that the A was approximately twice the value of the Z for an element. 1932 James Chadwick conducted experiments using radioactive material. Discovered a particle in the nucleus with no charge – called it the neutron.

57. Atomic Theory- Law of Definite Proportions Law of Definite Proportions: –A chemical compound has the same exact proportions by mass regardless of the size of the sample or source of the compound. –Ex: The composition of pure water H 2 O is ALWAYS be 11.2% hydrogen and 88.8% for oxygen by mass.

58. Example 1

59. Law of Definite Proportions Worksheet 1.Remember your Rules of Significant Figures 1.Multiply/Divide – Limiter is the value with least amount of sig figs. 2.Add/Subtract – Limiter is value with least amount of decimals. 2.When multiplying by 100%, the % sign is the unit of measure. Do not unit % key on calculator.

60. Example 2 A sample of sodium chloride NaCl weighing 175.35g contains 60.6% Cl by mass. 1.How many grams of Cl are in the sample? 2.How many grams of Na are in the sample?

61. Percent Composition Worksheet  You will need a Calculator and a Periodic Table. 1.For every compound determine how many atoms of each element are present. 2.Find the mass of each element in the compound on the P.T. (Round 2 decimal places) 3.Calculate the sum of the masses of the elements, call this the total mass. 4.Divide the mass of the element by the total mass, then multiply by 100%.

62. % Composition: Example

63. Laws Pertaining to Atomic Theory- Law of Multiple Proportions Law of Multiple Proportions –Is when 2 elements combine to form more than one compound. The ratio of the masses of the second element when combined with a certain mass of the first element is ALWAYS a ratio of the small whole numbers. –Ex:CO vs. CO 2. In CO 1.33g oxygen combine with 1g carbon, while in CO 2,there are 2.66g of oxygen that combine with 1g carbon.

64. Lesson 3 Counting Atoms Essential Question How do you distinguish between an atom, an ion, and an isotope? Objectives To calculate the atomic number, mass number, and average atomic mass. To explain what isotopes are.

65. ELEMENTS THAT EXIST AS DIATOMIC MOLECULES Remember: HOFBrINCl These elements only exist as PAIRS. Note that when they combine to make compounds, they are no longer elements so they are no longer in pairs! Hockey Stick and the Puck

66. ATOM COMPOSITION protons and neutrons in the nucleus.protons and neutrons in the nucleus. the number of electrons is equal to the number of protons.the number of electrons is equal to the number of protons. electrons in space around the nucleus.electrons in space around the nucleus. extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water.extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water. The atom is mostly empty space

67. ATOMIC COMPOSITION Protons (p + )Protons (p + ) –+ electrical charge –mass = 1.672623 x 10 -24 g –relative mass = 1.007 atomic mass units (amu) but we can round to 1 Electrons (e - )Electrons (e - ) – negative electrical charge –relative mass = 0.0005 amu but we can round to 0 Neutrons (n o )Neutrons (n o ) – no electrical charge –mass = 1.009 amu but we can round to 1

68. Atomic Number, Z All atoms of the same element have the same number of protons in the nucleus, Z 13 Al 27 Atomic number Symbol Mass Number

69. Mass Number, A C atom with 6 protons and 6 neutrons is the mass standardC atom with 6 protons and 6 neutrons is the mass standard = 12 atomic mass units= 12 atomic mass units Mass Number (A) = # protons + # neutronsMass Number (A) = # protons + # neutrons This is NOT on the periodic table…(that is the AVERAGE atomic mass)This is NOT on the periodic table…(that is the AVERAGE atomic mass) A boron atom has A = 5 p + 5 n = 10 amuA boron atom has A = 5 p + 5 n = 10 amu

70. Isotopes Atoms of the same element (same Z) but different mass number (A).Atoms of the same element (same Z) but different mass number (A). Boron-10 ( 10 B) has 5 p and 5 nBoron-10 ( 10 B) has 5 p and 5 n Boron-11 ( 11 B) has 5 p and 6 nBoron-11 ( 11 B) has 5 p and 6 n 10 B 11 B

71. Figure 3.10: Two isotopes of sodium.

72. Isotopes & Their Uses Bone scans with radioactive technetium-99.

73. Isotopes & Their Uses The tritium content of ground water is used to discover the source of the water, for example, in municipal water or the source of the steam from a volcano.

74. Atomic Symbols Show the name of the element, a hyphen, and the mass number in hyphen notation sodium-23 Show the mass number and atomic number in nuclear symbol form mass number 23 Na atomic number 11

75. Isotopes? Which of the following represent isotopes of the same element? Which element? 234 X 234 X 235 X 238 X 92 93 9292

76. Counting Protons, Neutrons, and Electrons Protons: Atomic Number (from periodic table) Neutrons: Mass Number minus the number of protons (mass number is protons and neutrons because the mass of electrons is negligible) Electrons: –If it’s an atom, the protons and electrons must be the SAME so that it is has a net charge of zero (equal numbers of + and -) –If it does NOT have an equal number of electrons, it is not an atom, it is an ION. For each negative charge, add an extra electron. For each positive charge, subtract an electron (Don’t add a proton!!! That changes the element!)

77. Learning Check 3a – Counting 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 these carbon atoms. 12 C 13 C 14 C 6 6 6 #p + _______ _______ _______ #n o _______ _______ _______ #e - _______ _______ _______

78. Learning Check 3b An atom has 14 protons and 20 neutrons. A.Its atomic number is 1) 142) 163) 34 B. Its mass number is 1) 142) 163) 34 C. The element is 1) Si2) Ca3) Se D.Another isotope of this element is 1) 34 X 2) 34 X 3) 36 X 16 14 14

79. IONS IONS are atoms or groups of atoms with a positive or negative charge.IONS are atoms or groups of atoms with a positive or negative charge. Taking away an electron from an atom gives a CATION with a positive chargeTaking away an electron from an atom gives a CATION with a positive charge Adding an electron to an atom gives an ANION with a negative charge.Adding an electron to an atom gives an ANION with a negative charge. To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na + Ca +2 I - O -2To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na + Ca +2 I - O -2 Na Ca I O Na Ca I O

80. Forming Cations & Anions A CATION forms when an atom loses one or more electrons. An ANION forms when an atom gains one or more electrons Mg --> Mg 2+ + 2 e- F + e- --> F -

81. PREDICTING ION CHARGES In general metals (Mg) lose electrons ---> cationsmetals (Mg) lose electrons ---> cations nonmetals (F) gain electrons ---> anionsnonmetals (F) gain electrons ---> anions

82. Charges on Common Ions +3 -4-2-3 +1 +2 By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.

83. Learning Check 3c – Counting State the number of protons, neutrons, and electrons in each of these ions. 39 K + 16 O -241 Ca +2 198 20 #p + ___________________ #n o ___________________ #e - ___________________

84. Learning Check 3d Write the nuclear symbol form for the following atoms or ions: A. 8 p +, 8 n, 8 e - ___________ B.17p +, 20n, 17e - ___________ C. 47p +, 60 n, 46 e - ___________

85. AVERAGE ATOMIC MASS Because of the existence of isotopes, the mass of a collection of atoms has an average value.Because of the existence of isotopes, the mass of a collection of atoms has an average value. Boron is 20% 10 B and 80% 11 B. That is, 11 B is 80 percent abundant on earth.Boron is 20% 10 B and 80% 11 B. That is, 11 B is 80 percent abundant on earth. For boron atomic weightFor boron atomic weight = 0.20 (10 amu) + 0.80 (11 amu) = 10.8 amu = 0.20 (10 amu) + 0.80 (11 amu) = 10.8 amu 10 B 11 B

86. Isotopes & Average Atomic Mass Because of the existence of isotopes, the mass of a collection of atoms has an average value.Because of the existence of isotopes, the mass of a collection of atoms has an average value. 6 Li = 7.5% abundant and 7 Li = 92.5% 6 Li = 7.5% abundant and 7 Li = 92.5% –Avg. Atomic mass of Li = ______________ 28 Si = 92.23%, 29 Si = 4.67%, 30 Si = 3.10% 28 Si = 92.23%, 29 Si = 4.67%, 30 Si = 3.10% –Avg. Atomic mass of Si = ______________

87. Lesson 4 Organizing the Periodic Table Essential Question How are elements grouped in the Periodic Table? Objectives To identify similar properties of elements in groups and periods.

88. Elements Element- atoms having an identical number of protons in each nucleus. Elements cannot be reduced to simpler substances by normal chemical means. Elements are organized into the Periodic Table of Elements by their Atomic Number 1 H 2 He 3 Li 4 Be 5 B 6 C 7 N

89. The Periodic Table

90. Periods in the Periodic Table

91. Groups in the Periodic Table Elements in groups react in similar ways!

92. Regions of the Periodic Table

93. Group 1A: Alkali Metals Cutting sodium metal Reaction of potassium + H 2 O

94. Magnesium Magnesium oxide Group 2A: Alkaline Earth Metals

95. Group 7A: The Halogens (salt makers) F, Cl, Br, I, At

96. Group 8A: The Noble (Inert) Gases He, Ne, Ar, Kr, Xe, Rn Lighter than air balloons “Neon” signs Very Unreactive because they have full electron levels XeOF 4

97. Transition Elements Lanthanides and actinides Iron in air gives iron(III) oxide

98. ELEMENTS THAT EXIST AS DIATOMIC MOLECULES Remember: BrINClHOF These elements only exist as PAIRS. Note that when they combine to make compounds, they are no longer elements so they are no longer in pairs! Hockey Stick and the Puck

99. Compounds Compounds are… –Substances that are made from atoms of two or more different elements chemically bonded together. –Ex: NaCl, CaCO 3

100. Molecules Molecules are… –Substances that are made from atoms of two or more alike or different element chemically bonded together. –Ex: O 2, H 2 (diatomics), NaCl