Structure of the Atom

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Structure of the Atom

• String theory ties it up!

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A History of Atomic Theory

• A brief look at the 2000-year long search for the
  
• building blocks of matter

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Modern Atomic Theory

• Atoms are the basic unit of matter.

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Modern Atomic Theory

• Atoms can be broken down into electrons, protons,
  and neutrons.

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Modern Atomic Theory

• The simplest atom is one proton and one electron.

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Modern Atomic Theory

• Electrons are negative and located in energy
  shells.
• Protons are positive and in the nucleus.
• Neutrons are neutral and in the nucleus,

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Smaller Subatomic Particles
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Quarks are charged.
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Question

• Why are protons positive?

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Modern Atomic Theory

• Protons can be further broken into up and down
  quarks.

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Quark Structure of Protons

• Protons are composed of two up quarks and one
  down quark.
• 2/3 e 2/3 e - 1/3 e 1 e
• Protons have a 1 e charge.

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Quark Structure of Protons

• Gluons hold the quarks together to make the
  proton.

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Question

• Why are neutrons neutral?

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Modern Atomic Theory

• Neutrons can be further broken into up and down
  quarks.

0
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Quark Structure of Neutrons

• Neutrons are composed of two down quarks and one
  up quark.
• 2/3 e - 1/3 e - 1/3 e 0 e
• Neutrons have a 0 e charge. Gluons hold the
  quarks together.

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Question

• Why do atoms with more than one proton need
  neutrons to be stable?

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• Like charges repel each other. Neutrons serve as
  a buffer so that the protons dont push each
  other apart.

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• The strong force holds the protons and neutrons
  together.
• This makes the nucleus dense.

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Question

• Why is the atom mostly empty space?

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• Electrons are negatively charged. They repel
  each other.

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Question

• If electrons repel each other, why dont they fly
  off into space?

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• A pair of electrons spin in opposite directions.
  This explains energy shell filling and the
  properties of metals.

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Question

• What holds the atom together?

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• Electrons are attracted to the oppositely charged
  protons. Repulsive forces among the electrons
  keep them from crashing into the nucleus. The
  attraction to the protons keeps the electrons in
  orbit.

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Question

• How do the sizes of the subatomic particles
  compare to each other?

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String Theory

• There are many more subatomic particles than just
  the 6 quarks.
• String Theory is the latest attempt to tie up the
  work of Newton and the work of Einstein.
• This will be the physics you learn in the future.

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Question

• Will this be on the quiz?

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What you need to know.

• Atoms are the basic complete unit of matter.
• Atoms are made of protons, neutrons, and
  electrons.
• Protons are positive and neutrons are neutral.
  They form the nucleus.
• Electrons are negative. They orbit the nucleus.

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Question

• Does this have anything to do with the periodic
  table of the elements?

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Modern Atomic Theory

• In any element, all the atoms have the same
  number of protons. Atoms with a different number
  of neutrons are called isotopes.

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Modern Atomic Theory

• Atoms of different elements are different.

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Modern Atomic Theory

• Atoms of two or more elements can combine to form
  compounds by sharing or transferring electrons.

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Modern Atomic Theory

• The atomic mass of an element reflects the
  average of all its isotopic forms, but is unique
  to the element.

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Modern Atomic Theory

• Atoms of elements in a compound combine in a
  constant ratio