Improvements • More info about the people, but take only 1-2 days to cover them Bell Work 12/9/13 • Start new bellwork titled “Atoms” 1.What do you remember about atoms? (their structure, the subatomic particles, the charges…) 2.W5SAYWoS Happy th 16 Birthday Kendle Rivera! Atoms: The Building Blocks of Matter • Prior knowledge • Today Schedule – Elements to memorize – Notes on history of atom – Worksheet • Monday – Electron configuration • Tuesday – Isotope quiz! Elements to Memorize • 1-20, 26-30, 47, 50, 78-80, 82 # Name Symbol How remember Today you are going to…take notes on the history of the atom. So you can…explain how & by whom the parts of the atom have been discovered. You’ll know you’ve got it when you can • List the scientists of the atom and their achievements History of Atom Overview Video • http://www.youtube.com/watch?v=B2aFTN hgyII&feature=related Leucippus & Democritus • Democritus 460 BC - 370 BC – Student of Leucippus – Believed all matter is made up of various imperishable, indivisible things which he called atoma, or “indivisible units” – Basically, they named the atom! Aristotle • 384 BC – 322 BC • Believed matter consisted of 4 basic elements • Wrong, but people believed him because he was popular with important people & the church. Alchemists • 1100’s • European “scientists” that tried to make gold from other metals – Couldn’t be done • Added ideas of observation & experimentation! • Recorded info on properties of matter Bell Work 12/10/13 1.What did Democritus think? 2.What did Aristotle think? 3.What did alchemist try to do? How did this advance science? John Dalton • 1766 – 1844 • Had a theory… Dalton’s Atomic Theory 1. All matter is composed of atoms 2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements are different 3. Atoms cannot be subdivided, created, or destroyed 4. Atoms of different elements combine in simple whole-number ratios to form compounds 5. In chemical reactions, atoms are combined, separated, or rearranged. Dalton’s Atomic Theory (Simplified) 1. All matter is composed of atoms 2. Atoms of same element are identical; atoms of different elements are different 3. Atoms cannot be subdivided, created, nor destroyed 4. Atoms of different elements combine to form compounds 5. In chemical reactions, atoms are rearranged. Modern Atomic Theory • Still True… – All matter is composed of atoms – Atoms of any one element differ in properties from atoms of another. • Different – Atoms of the same element may have different masses! (Called isotopes) – Atoms are divisible (not by ordinary chem. means). • Nuclear reactions! Discovery of the Electron In 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle...DISCOVERED THE ELECTRON!! Cathode ray tubes pass electricity through a gas that is contained at a very low pressure. Discovery of the Electron TV Demo! Cathode rays – stream of electrons e- moved ______________ the positive charged plate Some Modern Cathode Ray Tubes Conclusions from the Study of the Electron Cathode rays have identical properties regardless of the element used to produce them. All elements must contain identically charged electrons. Atoms are neutral, so there must be positive particles in the atom to balance the negative charge of the electrons J.J. Thomson’s Atomic Model I love me some plum puddin’! Discovered all electrons have equal charge, but couldn’t measure mass or charge of the electrons. Thomson believed that the electrons were like plums embedded in a positively charged “pudding,” thus it was called the “plum pudding” model. Mass of the Electron 1909 – Robert Millikan determines the mass of the electron. Enables him to calculate the charge too! The oil drop apparatus Mass of the electron is 9.109 x 10-31 kg Conclusions from the Study of the Electron Electrons have so little mass that atoms must contain other particles that account for most of the mass 1911: Rutherford’s Gold Foil Experiment Fired alpha particles (helium nuclei, ___ charge) Particles were fired at a thin sheet of gold foil Particle hits on the detecting screen (film) are recorded “Gold foil” demo Rutherford’s Findings Most of the particles passed right through A few particles were deflected VERY FEW were greatly deflected “Like howitzer shells bouncing off of tissue paper!” Conclusions: The nucleus is small The nucleus is dense The nucleus is positively charged Top of worksheet Bohr Model of Atom aka “planetary model” 1. Electrons assume only certain orbits around the nucleus. These orbits are stable and called "stationary" orbits. 2. Each orbit has an energy level associated with it. For example the orbit closest to the nucleus has an energy E1, the next closest E2 and so on. 3. Light is emitted when an electron jumps from a higher orbit to a lower orbit and absorbed when it jumps from a lower to higher orbit. 4. Energy of light emitted is the difference between the two orbit energies. Bohr Model of Atom aka “planetary model” 1st shell 2 e2nd shell 8 e3rd shell 8 e4th shell 18 e5th shell 18 e6th shell 32 e7th shell 32 e- Electron Cloud • More accurate • e- don’t travel in simple, specific orbits • e- travel around nucleus in random, unpredictable orbits at superfast speeds • Can’t tell exactly where they are, but they’re somewhere in the “e- cloud” Orbitals Electrons can be in 4 types of orbitals within an energy level… Named s, p, d, or f Don’t worry about them for now…we’ll talk more about them later. Bell Work 11/27/12 1.Discovered the nucleus 2.Planetary model of atom 3.Plum pudding model of atom 4.Discovered most of the atom is empty space 5.Cathode rays 6.Discovered electron 7.Gold foil experiment 8.W5SAYBoS Today you are going to…take notes on the parts of an atom & isotopes. So you can…explain the basic structure of an atom, which will help you to predict bonds in the future. You’ll know you’ve got it when you can • Identify all parts of an atom, their relative masses, charges, and location. (complete chart) • Determine the mass of an isotope Atom – smallest particle of an element that retains the chemical properties of that element. Composed of: protons neutrons electrons Protons Subatomic Particles Positive charge In nucleus (tiny, dense, center of atom) Mass of 1 amu (atomic mass unit) Neutrons Neutral (no charge) In nucleus Mass of 1 amu Electrons Negative charge In “electron cloud” around nucleus (“orbit” nucleus) Very little mass (about 1/2000 P, or 0.0006 amu) Atomic Particles Particle Charge Mass (kg) Location Electron -1 9.109 x 10-31 Electron cloud Proton +1 1.673 x 10-27 Nucleus 0 1.675 x 10-27 Nucleus Neutron Force in the Nucleus •Two protons extremely close to each other attract •(indirect effect of strong nuclear force, the strongest force in the universe!) •Over 100 protons can exist together in a nucleus! •Strong nuclear force has same effect on neutrons. “e-” Protons cathode rays “no” “p+” + charge Determines what element atom is no charge - charge Electron very little mass orbits nucleus subatomic particles found in atom charged about same mass Neutrons in nucleus Understanding Isotopes Atomic Number • Number of protons in an atom • Tells which element atom is – Atoms of the same element ALWAYS have the same number of protons. • Above atom on periodic table • What subatomic particles have the most mass? • What subatomic particle has hardly any mass? • Therefore, an atom’s mass depends on how many ___ and ___ it has. • All atoms of the same element have the same ____ ____, which means they have the same number of _____. • Do all atoms of the same element have the same mass? • What must be different about these atoms? • Atoms of the same element with a different number of neutrons are called isotopes. Isotopes Elements occur in nature as mixtures of isotopes. Isotopes are atoms of the same element that differ in the number of neutrons Isotopes are named by their mass number Isotopes atoms of same element with different number of neutrons and, therefore, different masses Isotope Protons Electrons Neutrons Hydrogen–1 (protium) 1 1 0 Hydrogen-2 (deuterium) 1 1 1 Hydrogen-3 (tritium) 1 1 2 Nucleus Mass Number •number of protons and neutrons in the nucleus of an atom. •measured in atomic mass units (amu) • 1 proton = 1 amu 1 neutron = 1 amu Mass # = p+ + n0 Assume the particles below are atoms, meaning they have no charge. Isotope p+ n0 e- Mass # Oxygen - 18 8 10 8 18 Arsenic - 75 33 42 33 75 Phosphorus - 31 15 16 15 31 Atomic Mass • average mass of all the naturally isotopes of that element • Found under symbol on periodic table Atomic mass of Carbon = 12.011 Symbol Composition of the nucleus % in nature Carbon-12 12C 6 protons 6 neutrons 98.89% Carbon-13 13C 6 protons 7 neutrons 1.11% Carbon-14 14C 6 protons 8 neutrons <0.01% Isotope Atomic Mass • average mass of all the naturally isotopes of that element • Also the mass of 1 mole of an element! There are two isotopic notations Element name – mass # or mass# Symbol atomic # Chlorine – 37 ___ protons ___ electrons ___ neutrons 108 Ag 47 ___ protons ___ electrons ___ neutrons Carbon – 10 ___ protons ___ electrons ___ neutrons Gold -200 ___ protons ___ electrons ___ neutrons 13 C 6 ___ protons ___ electrons ___ neutrons 197 Au 79 ___ protons ___ electrons ___ neutrons Sulfur-31 ___ protons ___ electrons ___ neutrons 197 Hg 80 ___ protons ___ electrons ___ neutrons Calcium-39 ___ protons ___ electrons ___ neutrons 19 F 9 Strontium-87 ___ protons ___ electrons ___ neutrons 119 Sn 50 Ions – charged atoms! • Charge of –2 has 2 more electrons than protons • Charge of +3 has 3 more protons than electrons Bell Ringer 12/5/12 Sulfur-31 ___ protons ___ electrons ___ neutrons 4. W5SAYW 197 Hg 80 ___ protons ___ electrons ___ neutrons Quiz answers Quiz answers Quiz answers Bell Work 12/7/12 1. What do you know about electron configuration? Bell Work 12/11/12 – 3 min Determine the number of electrons, protons, and neutrons in the following neutral atoms. 1. Helium-5 2. Sulphur-34 Bonus! • Empty 2 liter bottles • Big pop cans (the bigger the better) • Now lets review chart! Today you are going to…take notes on and begin writing the electron configuration of atoms So you can…better understand the structure of an atom and predict ionic bonds You’ll know you’ve got it when you can • Write the electron configurations and draw the Bohr models for – All elements to calcium – All atoms up to barium – All elements! Valence electrons • electrons in the outermost shell of an atom. • IMPORTANT! - determine many of the properties of an atom • What row? • What orbital (letter)? • How many over? Bell Work 12/13/12 • Turn in bonus • Write the electron configuration for 1.Bromine 2.Iodine 3.Astatine Valence electrons • electrons in the outermost shell of an atom. • IMPORTANT! - determine many of the properties of an atom Electron Configurations • Electron “locations” • Identifies which energy level the electrons are in • There are 4 orbitals – s, p, d, & f – s orbital, holds up to 2 electrons – p orbital, holds up to 6 electrons – d orbital, holds up to 10 electrons – f orbital, holds up to 14 electrons Electron Configuration Energy Level 2 1s Orbital # of electrons Bell Work 12/14/12 – 5 min • Turn in bonus • Write the electron configuration & Bohr diagram for 1. Fluorine-19 2. Bromine-80 3. Astatine-210 4.What are valence electrons? Schedule • • • • Bell work/check homework Grades Review homework Electron dot diagram Today you are going to…take notes on and begin writing the electron dot diagram of atoms So you can…better understand the structure of an atom and predict ionic bonds You’ll know you’ve got it when you can • Write the electron configurations, draw the Bohr models, and electron dot diagrams for – All elements! Electron Configuration Energy Level 1 3s Orbital # of electrons Electron Configuration 4 2p Energy level? Orbital? # of electrons? Beryllium (Be) – Atomic # 4 1s2, 2s2 Sulfur (S) 1s2, 2s2,2p6, 3s2, 3p4 Iron (Fe) – Atomic # 26 1s2, 2s2,2p6, 3s2, 3p6, 4s2, 3d6 Bohr Models • Where are the valence electrons? Homework (or Homeroom work) Write the electron configuration AND draw the following atoms • Helium-5 • Nitrogen-15 • Iron- 54 • Antimony-123 (symbol Sb) • BONUS CHART! Bell Work 12/11/12 Put your homework upside-down on your desk. Write the electron configuration AND draw the following atoms 1. Phosphorus-30 2. Cobalt-56 Bell Work 12/10/12 Put your homework upside-down on your desk. 1. Chlorine-36 2. Nickel-56 Electron Dot Diagram 1s2 Bell Work 12/20/12 Which numbers go together? 1.Discovered the nucleus 2.Planetary model of atom 3.Plum pudding model of atom 4.Discovered most of the atom is empty space 5.Cathode rays 6.Gold foil experiment 7.Discovered electron Which subatomic particles… + charge no charge - charge very little mass orbits nucleus found in atom subatomic particles charged about same mass in nucleus cathode rays “p+” “no” “e-” Atom & Solar System Similar little stuff (planets n e-) orbits big stuff both mostly empty space orbiting things are always moving Different orbits less precise in space solar system bigger! solar system has life some atomic particles have charges! planets have moons Atomic structure Proton - +, has mass of 1amu, in nucleus, always same # in atom! Neutron – neutral (no charge), 1 amu, in nucleus, different # in different atoms (isotopes) Electron – orbits nucleus, negative charge, 1/2000 mass of proton/nutron, can be lost through bonding Dalton’s Atomic Theory (Simplified) 1. All matter is composed of atoms 2. Atoms of same element are identical; atoms of different elements are different 3. Atoms cannot be subdivided, created, nor destroyed 4. Atoms of different elements combine to form compounds 5. In chemical reactions, atoms are rearranged. STOP Bromine-81 ___ protons ___ electrons ___ neutrons protons 40 Ar 18 ___ ___ electrons ___ neutrons Bell Ringer 11/14 – 5 minutes 1. The number of ___________ an atom has; gives it it’s identity. 2. Atoms of the same element that have a different number of neutrons are called ______________. 3. W5SAYW 4. Study Element Poster Project (33 pts) Chemical Symbol, average atomic mass, & atomic number _______ 3 points Electron configuration _______ 3 points All known isotopes ______ 2 points Electron Dot Diagram ______ 2 points At least 3 uses ______ 3 points Atomic Particles Particle Charge Mass (kg) Location Electron -1 9.109 x 10-31 Electron cloud Proton +1 1.673 x 10-27 Nucleus 0 1.675 x 10-27 Nucleus Neutron Bell Work •number of protons and neutrons in the nucleus of an atom. •measured in atomic mass units (amu) Mass # = p+ + n0 Assume the particles below are atoms, meaning they have no charge. Nuclide (new clyde) p+ n0 e- Mass # Oxygen - 17 8 9 8 17 Arsenic - 73 33 40 33 73 Phosphorus - 34 15 19 15 34 Bell Work 12/4 1. Atoms of the same element may have different numbers of ____________, and they may gain or lose ____________, but they ALWAYS have the same number of _____________. Bell Work 11/3 Protons Electrons “p+” + charge charged - charge very little mass cathode rays “e-” orbits nucleus about same mass sum gives atomic mass in nucleus subatomic particles found in atom no charge Neutrons sub “n0” a v Protons Neutrons Electron subatomic part charged + charge - charge no charge about same m very little ma in nucleus orbits nucle found in ato cathode ray “e-” “n0” “p+” subatomic particles charged + charge - charge no charge about same mass very little mass in nucleus orbits nucleus found in atom sum gives atomic mass cathode rays “e-” “n0” “p+” The Atomic Scale Most of the mass of the atom is in the nucleus (protons and neutrons) Electrons are found outside of the nucleus (the electron cloud) Most of the volume of the atom is empty space “q” is a particle called a “quark” Bell Work 11/4/10 1. How much would 1 gallon of mercury weigh? 2. If a 185 lb man on mercury, how much volume would you displace? (This is individual as it depends on your mass.) 3. How many m&m’s do you think are in the jar? Mercury has a density of 13.5 cm3. Use your conversion factors… Charge Charged atoms have an unequal number of protons & electrons and are called ions. Charge = p+ - e- Ion p+ N0 e- Oxygen 8 7 10 Sodium 11 12 10 Barium 56 65 Charge +2 Size of Atoms We think of the area occupied by electrons as an “electron cloud”. Radius of atom – distance from center of nucleus to outer part of e- cloud. Measured in picometers (pm) 1 pm = 10-12 m = 1/1,000,000,000,000 meter pm is to cm as cm is to km Nuclei are extremely dense… 200,000,000 metric ton/cm3 = 200,000,000,000 kg/cm3 weighs 440,000,000,000 lb/cm3 Bohr Model of Atom 1st shell 2 e2nd shell 8 e1. Find element’s atomic 3rd shell 8 enumber on p. table. 4th shell 18 e2. Draw nucleus & write 5th shell 18 e# of p+ & n0 6th shell 32 e• Mass # = p+ + n0 7th shell 32 e3. Draw electrons in 1. Helium – 5 orbitals 2. Beryllium – 11 3. Neon – 20 4. Carbon – 14 5. Potassium – 41 The Elements! 1 dozen = 12 1 gross = 144 1 ream = 500 1 mole = 6.02 x 1023 There are exactly 12 grams of carbon-12 in one mole of carbon-12. Bell Work 11/10 – 5 min Take out yesterday’s work. How many molecules of O2 are in 85.02 g of O2? (Use dimensional analysis to find your answer.) 1 mole O2 = 31.9988 g 1 mole = 6.02 x 1023 Avogadro’s Number 6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro (1776-1855). I didn’t discover it. Its just named after me! (Probably cuz I’m hot.) Amadeo Avogadro Calculations with Moles: Converting moles to grams How many grams of lithium are in 3.50 moles of lithium? 3.50 mol Li 6.941 g Li 1 mol Li = 24.2935 g Li 24.3 g Li Calculations with Moles: Converting grams to moles How many moles of lithium are in 18.2 grams of lithium? 18.2 g Li 1 mol Li 6.941 g Li = 2.62247 mol Li 2.62 mol Li Calculations with Moles: Using Avogadro’s Number How many atoms of lithium are in 3.50 moles of lithium? 3.50 mol Li 6.022 x 1023 atoms Li 1 mol Li = 21.077 x 1023 2.1077 x 1024 2.11 x 1024 2.11 x 1024 atoms Li Calculations with Moles: Using Avogadro’s Number How many atoms of lithium are in 18.2 g of lithium? 18.2 g Li 1 mol Li 6.94 g Li 6.022 x 1023 atoms Li 1 mol Li (18.2)(6.022 x 1023)/6.94 = 1.58 x 1024 atoms Li Bell Work 11/11 – 5 min Take out your homework. How many molecules of H2O are in 6,022 g of H2O? (Use dimensional analysis to find your answer.) Bell Work 11/15 – 5 min 6CO2 + 6H2O (+ light energy) C6H12O6 + 6O2 1. During photosythesis, a 1000 leaved plant produces about 1.429 g of O2 in an hour. Convert this to moles. 2. W5SAYW Mole Ratio 6CO2 + 6H2O (+ light energy) C6H12O6 + 6O2 According to the above equation... if 6 mol carbon dioxide are combined with 6 mol water, how many moles of glucose will be produced? How many moles of oxygen will be produced? This is called the mole ratio! Moles of one substance: moles of another Mole Ratio Cu(s) + 4HNO3(aq) Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l) In an experiment where nitric acid reacts with a penny, 3.100 g of copper (Cu) are lost and 4.489 g of nitrogen dioxide (NO2) are produced. What is the mole ratio of this reaction? To find the mole ratio, calculate how many moles of each participate in the reaction. Law of Conservation of Mass Mass is neither created nor destroyed during chemical or physical reactions. Total mass of reactants = Total mass of products Antoine Lavoisier Bell Work 11/17 – 5 min Take out mole conversions wksts 1 & 2. Turn your lab in if you haven’t already. 1. Calculate the number of molecules in 32.47 g of water. Calculations with Moles: Using Avogadro’s Number 1. Calculate the number of in 32.47 g of water. From periodic table: 1 mol H = 1.0079 1 mol O = 15.999 1 mol H2O = 2(1.0079 g) + 1(15.999 g) = 18.0148 g 32.47 g H2O 1 mol Li 6.022 x 1023 atoms H2O 18.0148 g H2O 1 mol H2O (32.47)(6.022 x 1023)/ 18.0148 = 1.085409 x 1024 1.085 x 1024 molecules H2O 1. How many moles of silver are in 57.00 g of Ag? From periodic table: 1 mol Ag = 107.87 g 57.00 g Ag X 1 mol Ag 1 107.87 g Ag 0.5284 mol Ag = 0.5284138 2. How many moles of gold are in 89.0 g of Au? From periodic table: 1 mol Au = 196.97 g 89.0 g Au 1 X 1 mol Au 196.97 g Au 0.452 mol Au = 0.4518454 3. How many moles of iron are in 2.43 x 1025 atoms of Fe? From your brain (Av’s #): 1 mol = 6.022 x 1023 2.43 x 1025 atoms Fe 1 mol Fe = 0.40352 x 102 X 1 6.022 x 1023 atoms Fe 4.04 x 101 mol Fe 40.4 mol Fe 4. How many atoms of copper are in 3.1 g of Cu? From periodic table: 1 mol Cu = 63.546 g From your brain (Av’s #): 1 mol = 6.022 x 1023 3.1 g Cu X 1 mol Cu X 6.022 x 1023 atoms Cu = 1 63.546 g Cu 1 mol Cu 0.29377 x 1023 2.9 x 1022 atoms Cu 5. How many molecules of carbon dioxide are in 86.00 g of CO2? From periodic table: 1 mol C = 12.011 g 1 mol O = 15.999 g Therefore: 1 mol CO2 = 1(12.011) + 2(15.999 ) = 44.009 g From your brain (Av’s #): 1 mol = 6.022 x 1023 86.00 g CO2 X 1 mol CO2 1 44.009 g CO2 X 6.022 x 1023 molecules CO2 1 mol CO2 11.77 x 1023 1.177 x 1024 molecules CO2 = 6. How many molecules of copper sulfate are in 8 g of CuSO4? From periodic table: 1 mol Cu = 63.546 g 1 mol S = 32.065 g 1 mol O = 15.999 g Therefore: 1 mol CuSO4 = 1(63.546) + 1(32.065 ) + 4(15.999) = 159.607 g From your brain (Av’s #): 1 mol = 6.022 x 1023 8 g CuSO4 X 1 mol CuSO4 X 1 159.607 g CuSO4 6.022 x 1023 molecules CuSO4 = 1 mol CuSO4 0.30184 x 1023 3 x 1022 molecules CuSO4 8. How many atoms of oxygen are in 2.0 mol of CO2? From chemical formula: there are 2 moles of O atoms for each mole of CO2 molecules 1 mol CO2 = 1 mol C 2.0 mol CO2 1 X 2 mol C 1 mol CO2 = 4 mol C 4.0 mol O 7. How many atoms of carbon are in 2.0 mol of CO2? From chemical formula: there are 1 mole of C atoms for each mole of CO2 molecules 1 mol CO2 = 1 mol C 2.0 mol CO2 1 X 1 mol C 1 mol CO2 X 6.022 x 1023 atoms C 1.2 x 1023 atoms 1 mol C 9. How many atoms of oxygen are in 86.00 g of CO2? (See # 5) From periodic table: 1 mol C = 12.011 g 1 mol O = 15.999 g Therefore: 1 mol CO2 = 1(12.011) + 2(15.999 ) = 44.009 g From your brain (Av’s #): 1 mol = 6.022 x 1023 86.00 g CO2 X 1 mol CO2 1 44.009 g CO2 X X 2 atoms CO2 1 molecule CO2 6.022 x 1023 molecules CO2 1 mol CO2 3.9082 x 1023 3.908 x 1023 molecules CO2 On Quiz Just like bohring worksheets! Test Tuesday Law of conservation of mass Atom Dalton’s atomic theory Isotopes Bohring worksheet Protons, neutrons, electrons (chart) Discovery of electron – who & how Plum pudding model Rutherford & gold foil experiment Bohring worksheets, # e- in each shell Avagadro’s number (memorized) Mole problems 1 mole ratio question 1 atomic mass unit - 1/12 the mass of a carbon-12 atom Molecular mass (m) of a substance is the mass of one molecule of that substance, in atomic mass units(s) u About Quarks… Protons and neutrons are NOT fundamental particles. Protons are made of two “up” quarks and one “down” quark. Neutrons are made of one “up” quark and two “down” quarks. Quarks are held together by “gluons” Protons Neutrons Electron subatomic part charged + charge - charge no charge about same m very little ma in nucleus orbits nucle found in ato cathode ray “e-” “n0” “p+” Bell Work 11/30/11 – 5 min 1. Who discovered the electron? 2. If a substance had a density of 200,000,000,000 kg/cm3, how much mass would be in a 32.7 cm3 sample? 3.One kilogram weighs 2.2 lbs. How much would the sample weigh? Bell Work 11/29/11 – 5 min 1. 25 m = ? km 2. Who named the atom? 3. W5SAYWorS Bell Work 11/23/11 – 5 min 1. What did J.J. Thomson discover? 2. Explain J.J. Thomson’s model of the atom. 3. What atom is represented in the Bhor diagram below?