2Greeks invented concept of Atom approximately 2500 years ago Later thought matter was made up of fire,water,air,earthLet’s call it … an atom.Definition of Atom:Smallest particle of an element that retains the chemical identity of the element
3Columbus Discovers the West Discovery Timeline400 B.C1700 A.D.1492 A.D.Greeks invent concept of atomColumbus Discovers the WestAbout late 1700s some new ideas through experiments came to be discussed.
4What Were Some of the Results of These Experiments? Law of Conservation of MassLaw of Constant Composition (also called Law of Definite Proportions)Law of Multiple Proportions
5Law of Conservation of Mass +=Matter is not created or destroyed in a chemical reaction
6Law of Constant Composition or Law of Definite Proportions A chemical has exactly the same proportions no matter the sizeExample:Doesn’t matter if 3 crystals or a jar of salt66 % of mass is always Chloride33 % of the mass is always SodiumORSame “Proportions”, Same “Composition”
7Example of the Law or Constant Composition (Law of Definite Proportions) What would happen if I take a small bite of cake or a GIANT bite of cake?Would it taste the same?The “Composition” of the cake is the same all the way through.A COMPOUND (like sugar or salt) is the SAME no matter where you find it, or how much you have.
8The Law of Multiple Proportions Chemicals always combine in ratios of small whole numbersExample:H2O - WaterThere will always be a 2 to 1 ratio between Hydrogen and OxygenWhether you have one water molecule or an ocean full water
9Law of Multiple Proportions Example Molecules are not made up of “1/2” or an atom or pieces of an atomThis proportion might be 1: 3/4Remember WHOLE numbers.
10Discovery Timeline Late 1700s 400 B.C 1803 1492 A.D.1803Greeks invent concept of atomColumbus Discovers the WestNew Experiments and LawsJohn Dalton and the Atomic Theory of Matter
11Jeopardy Slide - Dalton At age 12 Dalton was teaching the local schoolWas reading Newton’s Book in LatinColor Blindness was called “Daltonism” for a lengthy time
12John Dalton - 1803 Atomic Theory of Matter UNIQUE - Atoms are unique from other elementsGROUPS - Compounds are combined in small whole numbers.LAW OF CONSERVATION OF MATTER - atoms are rearranged or combined but not destroyedINDIVIDUALS - Elements are composed of atoms (smallest building block)
13Discovery Timeline Almost 1900 400 B.C 1803 Late 1700s400 B.C1492 A.D.1803Greeks invent concept of atomJohn Dalton and the Atomic Theory of MatterColumbus Discovers the WestNew Exper-iments and LawsThompson Discovers the Electron
14John Thompson, circa 1900 Discovers Electron Prior to this a man named Faraday hypothesized that atoms had a chargeThompson hypothesized that the electrical charge was negative and that the particle had mass
15Thompson’s Experiment using a Cathode Ray Tube (CRT) Elements are neutral (no charge)Thompson could alter path of particles by using magnets (that showed they had a charge)The type of magnet showed that it had a negative chargebatterymagnets
16Thompson (continued)Now Thompson knew that there was a negative particle in the atom but where???I’m tired…
17Discovery Timeline 400 B.C 1910 Rutherford discovers the nucleus Late 1700s400 B.C1492 A.D.Almost 190018031910Greeks invent concept of atomJohn Dalton and the Atomic Theory of MatterThomp-son Dis-covers the ElectronColumbus Discovers the WestNew Exper-iments and LawsRutherford discovers the nucleus
18Jeopardy Slide Rutherford Rutherford was not a brilliant man, often getting lost in Math, not terribly clever in experimentation, just tenacious and open-mindedHis assistant was Hans Geiger, inventer of the “Geiger Counter”
19Rutherford’s Model of the Atom Rutherford hypothesized that the inside of an atom was a mass with bits of matter mixed in.Yum Yum!He called the model the “Plum Pudding” Model
20Rutherford’s Gold Foil Experiment Rutherford set up very thin gold foil as a target“shot” positive charges to foilWatched patterns that positive particles made
21Results of the Rutherford’s Experiment Alpha particles (positive particles) went throughOnly sometimes ‘bounced” backProved that nucleus was mostly empty spaceCalled center “nucleus”
22Rutherford’s NEW Model of the Atom Rutherford hypothesized that the inside of an atom was a small mass called a nucleus.Yuck!
28Daltons Theory of Matter UGLIU Unique (Elements are..)G Groups (They are grouped in small whole number groups Law of Multiple Proportions)L Law of Conservation of MatterI Individual (Matter is made up of individual atoms)