Atomic Structure

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Atomic Structure
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History

• 400 B.C. Democritus proposed all matter was
  made up of small particles called atoms
• Atomic numbers were assigned to elements by Henry
  Moseley
• 1913- Niels Bohr described the planetary model of
  the atom

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Planetary model
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The Shell Model

• The more accurate model puts a cloud around the
  nucleus and electrons move about in shells
• Each shell can hold so many electrons
• Little energy in the most inner shell so only 2
  electrons can be found there.
• The farther you get from the nucleus, the more
  electrons a shell can hold

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The atoms makeup

• This shell model of a hydrogen atom or lead atom
  is made up of the same general parts.
• A nucleus made up of protons (1 in Hydrogen and
  82 in Lead) and neutrons (usually the same amount
  as the protons)
• Floating around the nucleus are electrons

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Mass of Subatomic Particles

• Particle Charge Mass compared Actual Mass
• to electron
• Electron Negative 1 9.11x10-31
• Proton Positive 1836 1.673x10-27
• Neutron Neutral 1841 1.675x10-27

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Charges

• The three subatomic particles as they are called
  have different charges
• Protons- ()
• Neutrons- no charge
• Electrons- (-)

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Atomic Mass

• The mass of an atom is equal to the number of
  protons and neutrons found in the nucleus
• If an atom of carbon has 6 protons and 6
  neutrons, its mass is 12

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Atomic Number

• The atomic number found above the chemical symbol
  is equal to the number of protons the atom has
• An atom with 19 protons has to be potassium (K)

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Chemical Names

• Why is Co different from CO?
• Co is Cobalt
• CO is carbon monoxide
• Be sure to use upper and lower case properly

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Isotopes

• Atoms of the same element that have different
  numbers of neutrons are called isotopes
• Hydrogen can have 0, 1, or 2 neutrons in its
  nucleus

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Misc. Facts

• Hydrogen is the most abundant element. It makes
  up almost 90 of all atoms. As well it was the
  1st element to exist
• Fused hydrogen atoms formed inside stars and this
  created the other elements
• Most atoms formed when the universe began and are
  constantly being recycled
• Atoms that make up you are billions of years old

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Chapter Review (class work)

• Try to complete 5, 6, and 7.

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Protons have a positive charge

1. True
2. False

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C-12 is a radioactive isotope used in carbon
dating fossils

1. True
2. False

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The charge of a neutron is

1. negative
2. No charge

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The number of electrons that can fit in the 1st
shell is

1. 8
2. 2
3. 18

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The electron has more mass than the proton and
neutron

1. Yes
2. No

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The atomic number of carbon is

1. 12.01115
2. 12
3. 6
4. C

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The element symbol of helium is

1. H
2. 2
3. He
4. Helium

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The mass number of C-14 is 14

1. True
2. False

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Play-doh Lab

• Partner up
• Create a 3 dimensional model of an atom using
  play-doh and beads. It must be the shell model
• Your atom must have an atomic number between 6
  and 12.
• On a separate sheet draw your atom and label the
  following Protons, neutrons, electrons, nucleus,
  electron cloud, any and all shells
• Write down the name, atomic number, atomic mass,
  and symbol