Structure of an Atom

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Structure of an Atom

• When you read the Periodic Table, one of the most
  common questions is, Why do the names not match
  the symbol? The reason is that the names do
  match the symbol, but it is the Latin name.

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Example

• Silver
• Symbol Ag
• Latin Name Argentum

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Atomic Components

• An element is matter that is composed of one type
  of atom, which is the smallest piece of matter
  that still retains the property of the element.

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The parts

• Atoms are composed of particles called
• Protons ()
• Neutrons (no charge)
• Electrons (-)

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The Mass

• Protons and Neutrons are found in a small,
  positively charged () center of the atom called
  the nucleus that is surrounded by a cloud
  containing electrons.
• (If both protons and neutrons are found in the
  nucleus, why is it positive ()?)

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Diagram

• Protons positively charge 1
• Neutrons do not have a charge (o)
• Electrons negatively charge 1-
• Atoms of different elements differ in the number
  of protons they contain.

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New Material - Quarks

• Even Smaller
• Protons and Neutrons are made up of smaller
  particles called quarks. Scientists have
  confirmed the existence of six uniquely different
  quarks. Scientists theorize that the arrangement
  of three quarks held together with the strong
  nuclear force produces a proton. 3 more makes a
  neutron.

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Quarks -
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Quarks

• To find quarks, scientists accelerate charged
  particles to tremendous speeds then force them to
  collide with other protons.

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Models

• Scientists use models to represent things that
  are difficult to visualize, (that means see in
  your mind)

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Atoms

• Atoms are very small. It would take about 24,400
  atoms staked on top of each other to equal the
  thinness of a sheet of aluminum foil.
• To study them, scientists developed models that
  they can use to visualize how the atom is
  constructed

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The Model has changed.

• Democritus proposed the idea that atoms make up
  all substance in
• 400 B.C.
• But Aristotle disputed Democritus Theory saying
  that all matter is uniform throughout and not
  composed of smaller particles.

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Aristotles Theory

• Aristotles Idea was accepted for over 2000
  years.
• See what happens when you dont study before you
  say things. They tend to be WRONG!!
• Anyhow, he didnt have the technology that we
  have today either.

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John Dalton

• In the 1800s John Dalton provided a model of the
  atom as a solid sphere.

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• But over time and experiments, scientists have
  modified the atomic model. The model that we use
  today is the accumulated knowledge of almost 200
  years.

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Thompson s Model

• The chocolate chip cookie model
• Whats missing?

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Rutherfords Atom

• Whats missing?

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Bohr Model

• Diagram like planets orbitals.

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Electron Cloud

• Newest Model

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Electron Cloud

• Developed in 1926, the electron cloud is the area
  around the nucleus of an atom where its electrons
  are most likely found.
• The electron cloud is 100,000 times larger than
  the diameter of the nucleus, but an electron is
  much smaller than a proton

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The atoms mass

• Proton 2000 times larger than an electron.
• Electrons the electron cloud makes up an atoms
  volume. (space) Electrons are very tiny.

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Why we dont see them.

• Because an electrons mass is small and the
  electron is moving so quickly around the nucleus,
  it is impossible to describe its exact location
  in the atom.

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What do electrons do?

• Each electron travels at an average distance form
  the nucleus, depending on its energy.
• These average distances are referred to as energy
  levels.
• Energy levels are areas of the cloud where the
  electrons are more likely to be found.

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Energy Levels