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4.1 Defining the Atom Early Models Democritus (about 400BC)matter composed of tiny, indivisible particles QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Dalton (about 1800)- - used scientific method transformed Democritus’ ideas into theory QuickTime™ and a TIF F (Uncompressed) decompressor are needed to see this picture. 4.1 Defining the Atom QuickTime™ and a Sorenson Video 3 decompressor are needed to see this picture. Atoms of element A are identical Atoms of element B are identical, but different than A and BA element Atoms of element A and B can be can be physically chemically combined mixed together as a compound Dalton Proposed 1.All elements composed of tiny, indivisible particles 2. Atoms of an element are identical & distinct from atoms of other elements 3. Atoms can form compounds, combining in simple whole-number ratios 4. Atoms can be rearranged (chemical reactions), but atoms of one element do not change into atoms of another element. Sizing Up the Atom 5x10-11 - 2x10-10m Atoms cannot be seen with a light microscope A tunnelling electron microscope can make images of atoms like this: Tunnelling Electron Microscope Atoms cannot be seen with a light microscope Tunnelling Electron Microscope Atoms cannot be seen with a light microscope QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Chemistry Warm Up Chapter 4 Scavenger Hunt. 1. Copy this table and fill in the missing information: Name of Particle Mass Relative Charge to a Proton Location in the Atom 2. Given that 1 mile = 5280 feet, Use conversion factors and dimensional analysis to calculate the number of miles in 12 427 inches. Show all your work, conversion factors and proper cross-canceling of units. Chemistry Warm Up Chapter 7 Scavenger Hunt. 1. Copy this table and fill in the missing information: Name of Particle Mass Relative Charge to a Proton Location in the Atom Proton 1 1+ Nucleus Neutron >1 0 Nucleus 1- Around nucleus Electron 1/1840 2. Given that 1 mile = 5280 feet, Use conversion factors and dimensional analysis to calculate the number of miles in 12 427 inches. Show all your work, conversion factors and proper cross-canceling of units. Chemistry WarmUp Copy ALL of these assignments into your binder Including dates, WarmUps, InClass assignments AND page numbers! September 28-29 WarmUp: Agenda / Isotope Introduction InClass: The Black Box p108 Demo: Observing Cathode Rays p105TE InClass Periodic Table 101 Homework Key Concepts 4.2 and 4.3 DUE NEXT CLASS September 30 WarmUp: questions q21-24p116-117 InClass: Dimensional Analysis Practice Homework: Complete notes 5.1 answer q1-7p132 DUE NEXT CLASS October 1-2 WarmUp: Ms Lyall’s Periodic Table Scavenger Hunt Test: Chapters 1-3 InClass: The Wintergreen Lifesaver Effect. Urban Legend? We find out. InClass: Electron Configuration Worksheet Demo: Atomic Emission Spectra p137 (adapted) Homework: Complete notes 5.2 answer q8-9p135 DUE NEXT CLASS When you finish, read 4.2 and complete your notes. 4.2 Structure of the Nuclear Atom Subatomic Particles Atoms not indivisible Electrons Protons Neutrons Electrons Discovered 1897 by J.J.Thomson QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Used cathode ray tube to show electrons are negatively charged Electrons Discovered 1897 by J.J.Thomson Used cathode ray tube to show electrons are negatively charged Deflected by magnet Electrons Discovered 1897 by J.J.Thomson Used cathode ray tube to show electrons are negatively charged Deflected by electrical charge Electrons Discovered 1897 by J.J.Thomson Calculated charge/mass ratio The ratio of charge to mass was the same, regardless of gas in cathode tube. Conclusion? Electrons must be present and the same in all elements. Electrons QuickTime™ and a Sorenson Video 3 decompressor are needed to see this picture. Electrons Robert A Millikan 1916 oil drop experiment QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Millikan calculated the mass of an electron Mass or electron = 1/1840 mass of a hydrogen atom Charge = -1 Electrons Robert A Millikan 1916 oil drop QuickTi me™ and a TIFF ( Uncompressed) decompressor are needed to see thi s pi ctur e. experiment QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. The actual apparatus used in the Millikan oil drop experiment Neutrons and Protons Atoms are neutral When charges do exist, they are always in simple multiples of the charge on an electron (no fractions) Eugen Goldstein 1886 found cathode ray evidence of protons Proton- charge of +1 mass 1840 times mass of electron (1 atomic mass unit) Neutrons and Protons Neutrons Not discovered until 1932 by James Chadwick Quic kTime™ and a TIFF (Unc ompres sed) dec ompres sor are needed to see this pic ture. Neutrons have no charge have a mass similar to proton Atomic Nucleus “Plum pudding,” model Electron, “raisins,” stuck in a lump of positive, “dough.” QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Disproved in 1911 by one of Thomson’s students, Ernest Rutherford QuickTi me™ a nd a TIFF (Uncompre ssed ) decomp resso r are need ed to se e th is p icture. Rutherford’s Gold Foil Experiment Alpha particles shot at a thin piece of gold foil did not pass right through with slight deflection. Instead, most passed straight through. Some bounced right back! Rutherford’s Gold Foil Experiment Rutherford concluded that •Most of the atom is empty space •All of the positive charge and almost all of the mass is Concentrated in the tiny core, “nucleus.” composed of protons and neutrons. An idea of the size: Atom = football stadium Nucleus = marble 4.3 Distinguishing Atoms Atomic number = number of protons Defines the element! Atoms are electrically neutral therefore atomic number also is the number of electrons p111 problem 15 15 complete the table: Element Atomic # Protons K 19 19 19 B 5 5 5 S 16 16 16 V 23 23 Electrons 23 p111 problem 16 16 How many protons and electrons? a.Fluorine 9 b. Calcium 20 c. Aluminium 13 (Atomic) Mass Number number of protons + number of neutrons = mass number Therefore mass number - number of protons = number of neutrons Helium with a mass number of 4 has 2 protons. How many neutrons does it 2 neutrons have? Isotope Notation mass number (number of protons + neutrons) 197 79 Au symbol First letter always capitalized Second letter never capitalized atomic number (number of protons) How many neutrons does an atom of gold-197 have? 118 neutrons How many neutrons p112 q17 a. 16 8 O b. 8 neutrons d. 32 16 S c. 108 47 61 neutrons 16 neutrons 80 35 Br 45 neutrons e. Ag 207 82 Pb 125 neutrons Express in Isotope Notation p112 q18 a. Carbon-12 12 6 C F a. Fluorine-19 19 9 a. Beryllium-9 9 4 Be Express in Isotope Notation p112 q18 a. Carbon-12 12 6 C F a. Fluorine-19 19 9 a. Beryllium-9 9 4 Be Isotopes 20 Neon-20 Neon-21 Neon-22 Ne 21 10 Ne 22 10 Ne 10 10 neutrons 11 neutrons 12 neutrons Isotopes have different # of neutrons, same # of protons and electrons Q19 p113 Use isotope notation to show Oxygen-16 16 8 O Oxygen-17 17 8 O Oxygen 18 18 8 O Q12 How many neutrons in each?(Chromium’s atomic number=24) Chromium-50 26 neutrons Chromium-52 28 neutrons Chromium-53 29 neutrons Atomic Mass Atomic Mass Unit 1/12 mass of an atom of carbon-12 Since carbon 12 has 6 protons and 6 neutrons, Mass of 1 proton is about 1amu Why isn’t the atomic mass = atomic mass number? Atomic Mass Weighted average of the mass of all naturally occurring isotopes. To find atomic mass, calculate (Mass of isotope)•(%abundance as decimal) For each isotope And add the results together Atomic Mass Carbon is 98.89% Carbon-12 & 1.11% Carbon-13 Its atomic mass would be (12amu•0.9889)+(13.03amu•0.0111) = 12.011 amu Chemistry Warm Up questions q21-24p116-117 You CAN do this. Work out the example if you are stuck. It’s like this: Carbon is made up of 98.89% Carbon-12 & 1.11% Carbon-13 Its atomic mass would be (12amu•0.9889)+(13.03amu•0.0111) = 12.011 amu Chemistry Warm Up questions q22-24 p149 Try to answer these without your notes or the book, then go back and check your answers against your notes or the book. When you finish, complete the second version of Reading & Processing Information from the Periodic Table (worksheet) Chapter 4 Review 1. Make a sketch of an atom of Lithium-6. Label the 3 main subatomic particles. 2. What is the mass number of the atom you drew in question 1? How do you know? 3. Invent an isotope of the atom you drew above make a labeled drawing of it. How do you know it is an isotope? 4. Make a labeled drawing of Thomson’s cathode ray tube experiment. What did he discover? 5. Make a labeled drawing of Rutherford’s gold foil experiment. What important hypothesis did Rutherford propose? 6. What is an atomic mass unit? 7. Based on the correct answer to question 6, one might expect carbon’s atomic mass to be 12.000. Why does the periodic table list carbon’s atomic mass as 12.011? 8. Show, with an example, how atomic mass is calculated. Chapter 4 Review Worksheet 1. Make a sketch of an atom of Lithium-6. Label the 3 main subatomic particles. Chapter 4 Review Worksheet 2. What is the mass number of the atom you drew in question 1? How do you know? The mass number is 3. All lithium has 3 protons. That’s its atomic number. Lithium-6 has a mass number of 6. The mass number is the number of protons + neutrons. 6 protons + neutrons - 3 protons = 3 neutrons 3. Invent an isotope of the atom you drew above make a labeled drawing of it. How do you know it is an isotope? An isotope has the same atomic number with a different number of neutrons (therefore a different mass number). Chapter 4 Review Worksheet 4. Make a labeled drawing of Thomson’s cathode ray tube experiment. What did he discover? Thomson is credited with discovering a very, very small sub atomic particle with a negative charge, the electron. Chapter 4 Review Worksheet 5. Make a labeled drawing of Rutherford’s gold foil experiment. What important hypothesis did Rutherford propose? Rutherford is credited with discovering the nuclear atom. His hypothesis is that the atom contains a relatively small nucleus which contains all of the positive charge and almost all of the mass of the atom. Chapter 4 Review Worksheet 6. What is an atomic mass unit? An atomic mass unit is equal to 1/12 the mass of an atom of carbon12. Chapter 4 Review Worksheet 7. Based on the correct answer to question 6, one might expect carbon’s atomic mass to be 12.000. Why does the periodic table list carbon’s atomic mass as 12.011? Atomic mass takes into account all the isotopes of an element. Atomic mass is the weighted average of all the naturally occuring isotopes of an element. 8. Show, with an example, how atomic mass is calculated. (12.00amu x .99) + (13.00amu x 0.01) = 12.01amu Periodic Table Horizontal row = period Atomic number increases left to right Atomic number increases as you go down Properties vary as you go across a period Vertical column = group Groups have similar chemical properties