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Atoms

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Atoms 400 b.c. Greeks Greeks philosophers ponder the nature of matter: what is it made of? Democritus: basic particle of matter = atom which means indivisble . – PowerPoint PPT presentation

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Title: Atoms


1
Atoms
2
400 b.c. Greeks
  • Greeks philosophers ponder the nature of matter
    what is it made of?
  • Democritus basic particle of matter atom
    which means indivisble.
  • Envisions these to be hard spheres
  • Aristotle does not believe in atoms

3
Daltons Atomic Theory1803
  • 1) All matter is composed of extremely small
    particles called atoms

4
Daltons Atomic Theory1803
  • Atoms of one element are all alike
  • (size, mass)

5
Daltons Atomic Theory1803
  • 3) Atoms cant be created, destroyed or
    subdivided

6
Daltons Atomic Theory1803
  • Atoms of different elements combine in
  • simple whole number ratios to form
  • compounds

7
Daltons Atomic Theory1803
  • 5) In a chemical reaction, atoms are combined,
    separated, or rearranged

8
Conservation of massin chemical reactions
9
Conservation of massin chemical reactions
10
1897 J.J. Thompson Cathode Ray Experiments
  • The electron is discovered.
  • PLUM PUDDING model

11
Rutherfords Gold Foil Experiment1909
  • Ernst Rutherford bombards a piece of gold foil
    with positively charged alpha particles (the
    nucleus of a helium atom)

12
Some alpha particles bounce back
13
Rutherfords Gold Foil Experiment
  • Observations
  • Most of the alpha particles passed straight
    through the gold foil as if it wasnt even there!
  • The nucleus of the atom is small, dense, and
    positively charged

14
Rutherfords Gold Foil Experiment
  • Interpretation (conclusions)
  • Atoms are mostly empty space and therefore MATTER
    is mostly empty space
  • Atoms have a small, dense, positively charged
    nucleus

15



This alpha particle passes through the
atoms empty space



Alpha particles have charge two charges will
repel each other
16
Subatomic Particles(Table O)
Proton
Electron
Neutron
17
Protons
  • Located in the atoms nucleus
  • Positive charge 1
  • Mass 1 amu (Atomic Mass Unit)

18
Neutrons
  • Located in the atoms nucleus
  • zero charge (neutral)
  • Mass 1 amu (Atomic Mass Unit)

19
Electrons
  • Located in the electron cloud outside the nucleus
  • Negative charge -1
  • Mass 1/1836 amu (negligible)

20
What are the subatomic particles in lithium and
carbon?
21
Models of the atom
22
A model of the atom to scale
  • If YOU are the nucleus of an atom, your closest
    electron would be.
  • ..in downtown Rhinebeck!

23
Actual image of 2 atoms
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