The Atom, in a nutshell

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The Atom, in a nutshell
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Democritus (c. 460370 BC)
Greek philosopher The name atom was his idea Proposed matter is made up of small particles Atoms comes from atomosindivisible Atoms differ in size and shape and combine in different ways, constantly moving
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John Dalton (17661844)
English chemist physicist, self educated published Atomic Theory Each element made of really small particles called atoms All atoms of a given element are identical Atoms of different elements have different properties, like mass and chemical reactivity Atoms arent changed by chemical reactions, just rearranged
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J.J. Thomson (18561940)

• Identified the electron using cathode ray tube,
  determined negative charge
• Atom is neutral, with a positive sphere and
  negative electrons embedded called the plum
  pudding model. Yum.
• The television and computer monitors use this
  technology even today.

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Ernest Rutherford (18711937)

• Gold Foil Experimentbombarded gold foil with
  radioactive particles, most passed through, some
  bounced back!
• Conclusions
• Some parts of atom must be more dense.
• New picture of the atom dense at the center,
  electrons on the outside
• Atom mostly empty space, most of mass found in
  the centernucleus with positively charged
  protons
• Hyperlink to demo

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Niels Bohr (18851962)

• Used light and observed the way light interacts
  only with specific energies determined the
  electrons are in specific levels
• Electrons moving around nucleus in fixed orbits
  w/fixed energy
• Sometimes called the planetary model
• Not completely accurate with how electrons are
  truly arranged

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Other Scientists

• Louis de Broglie (18921987) mathematical
  description of electrons in atoms
• James Chadwick (18911974) discovered the
  neutron around 1932, another massive particle in
  the nucleus

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Basics on the atom

• Three kinds of subatomic particles are electrons,
  protons, and neutrons.
• The nucleus is the center area of an atom and
  contains most of its mass
• Protons and neutrons are found in the nucleus.
  Each has a mass of 1 amu
• Electrons are found in levels outside of the
  nucleus

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Summary of particles
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The number of protons are equal to the number of
electrons in an atom so
Put a number where there is a letter.
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Answers
All of the numbers have to be the SAME!
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Answers
19
B
5
5
16
16
23
23
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Finding the amount of neutrons is a bit more work
This is called the isotope notation.
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The notation means
Lithium - 7
Mass number, A Protons and neutrons added together
7
3
4
Atomic number, Z Number of protons only
This particular atom has 4 neutrons.
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The notation means
Lithium - 6
Mass number Protons and neutrons added together
6
3
3
Atomic number Number of protons only
This particular atom has 3 neutrons.
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Both of these atoms would have the same chemical
properties, but one is slightly heavier than the
other. They are Isotopes.
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Hint always find the atomic number FIRST then
make protons and electrons equal to that!
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9
9
Neutrons mass atomic ?

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9
9
Neutrons mass atomic 10 ?
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What does the ? equal?
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9
19
9
F
21
9
19
9
F
14
29
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Si
22
22
25
Ti
25
30
Mn
25
22
Other demos -

• Link
• Fun facts about atomic particles
• Modern view of atom