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History of Elementary Particles

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Presentation on theme: "History of Elementary Particles"— Presentation transcript:

1 History of Elementary Particles

2 Greeks invented concept of Atom approximately 2500 years ago
Later thought matter was made up of fire,water,air,earth Let’s call it … an atom. Definition of Atom: Smallest particle of an element that retains the chemical identity of the element

3 Columbus Discovers the West
Discovery Timeline 400 B.C 1700 A.D. 1492 A.D. Greeks invent concept of atom Columbus Discovers the West About late 1700s some new ideas through experiments came to be discussed.

4 What Were Some of the Results of These Experiments?
Law of Conservation of Mass Law of Constant Composition (also called Law of Definite Proportions) Law of Multiple Proportions

5 Law of Conservation of Mass
+ = Matter is not created or destroyed in a chemical reaction

6 Law of Constant Composition or Law of Definite Proportions
A chemical has exactly the same proportions no matter the size Example: Doesn’t matter if 3 crystals or a jar of salt 66 % of mass is always Chloride 33 % of the mass is always Sodium OR Same “Proportions”, Same “Composition”

7 Example 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.

8 The Law of Multiple Proportions
Chemicals always combine in ratios of small whole numbers Example: H2O - Water There will always be a 2 to 1 ratio between Hydrogen and Oxygen Whether you have one water molecule or an ocean full water

9 Law of Multiple Proportions Example
Molecules are not made up of “1/2” or an atom or pieces of an atom This proportion might be 1: 3/4 Remember WHOLE numbers.

10 Discovery Timeline Late 1700s 400 B.C 1803
1492 A.D. 1803 Greeks invent concept of atom Columbus Discovers the West New Experiments and Laws John Dalton and the Atomic Theory of Matter

11 Jeopardy Slide - Dalton
At age 12 Dalton was teaching the local school Was reading Newton’s Book in Latin Color Blindness was called “Daltonism” for a lengthy time

12 John Dalton - 1803 Atomic Theory of Matter
UNIQUE - Atoms are unique from other elements GROUPS - Compounds are combined in small whole numbers. LAW OF CONSERVATION OF MATTER - atoms are rearranged or combined but not destroyed INDIVIDUALS - Elements are composed of atoms (smallest building block)

13 Discovery Timeline Almost 1900 400 B.C 1803
Late 1700s 400 B.C 1492 A.D. 1803 Greeks invent concept of atom John Dalton and the Atomic Theory of Matter Columbus Discovers the West New Exper-iments and Laws Thompson Discovers the Electron

14 John Thompson, circa 1900 Discovers Electron
Prior to this a man named Faraday hypothesized that atoms had a charge Thompson hypothesized that the electrical charge was negative and that the particle had mass

15 Thompson’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 charge battery magnets

16 Thompson (continued) Now Thompson knew that there was a negative particle in the atom but where??? I’m tired…

17 Discovery Timeline 400 B.C 1910 Rutherford discovers the nucleus
Late 1700s 400 B.C 1492 A.D. Almost 1900 1803 1910 Greeks invent concept of atom John Dalton and the Atomic Theory of Matter Thomp-son Dis-covers the Electron Columbus Discovers the West New Exper-iments and Laws Rutherford discovers the nucleus

18 Jeopardy Slide Rutherford
Rutherford was not a brilliant man, often getting lost in Math, not terribly clever in experimentation, just tenacious and open-minded His assistant was Hans Geiger, inventer of the “Geiger Counter”

19 Rutherford’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

20 Rutherford’s Gold Foil Experiment
Rutherford set up very thin gold foil as a target “shot” positive charges to foil Watched patterns that positive particles made

21 Results of the Rutherford’s Experiment
Alpha particles (positive particles) went through Only sometimes ‘bounced” back Proved that nucleus was mostly empty space Called center “nucleus”

22 Rutherford’s NEW Model of the Atom
Rutherford hypothesized that the inside of an atom was a small mass called a nucleus. Yuck!

23 Rutherford’s Gold Foil Experiment Animation

24 What Do I Need to Remember ?
Greeks came up with Atom 3 Laws that started it all… Dalton - Atomic Theory of Matter Thompson CRT Experiment Rutherford’s Gold Foil Experiment

25 Memory Helps Rutherford A Ford Truck carrying Plum Pudding
Covered in Gold Foil Discovered the Nucleus I’d “Rather” have a Ford (Rutherford)

26 3 Laws Always Whole #s One You Already Know…
Law of Conservation of Matter Law of Definite Proportions Law of Multiple Proportions

27 Thompson Cathode Ray Tube

28 Daltons Theory of Matter
UGLI U Unique (Elements are..) G Groups (They are grouped in small whole number groups Law of Multiple Proportions) L Law of Conservation of Matter I Individual (Matter is made up of individual atoms)


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