5.2 and 5.3

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5.2 and 5.3

• Bohr vs the quantum mechanical model of the atom

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5.2 and 5.3 Bohr and the quantum mechanical model

• Compare the Bohr and quantum mechanical models of
  the atom.

• Explain the impact of de Broglie's wave article
  duality and the Heisenberg uncertainty principle
  on the current view of electrons in atoms.
• Identify the relationships among a hydrogen
  atom's energy levels, sublevels, and atomic
  orbitals.

atom the smallest particle of an element that
retains all the properties of that element, is
composed of electrons, protons, and neutrons.
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Section 5.2 Quantum Theory and the Atom (cont.)
ground state quantum number de Broglie
equation Heisenberg uncertainty principle
quantum mechanical model of the atom atomic
orbital principal quantum number principal energy
level energy sublevel
Wavelike properties of electrons help relate
atomic emission spectra, energy states of atoms,
and atomic orbitals.
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Review Electrons (ground state and excited state)
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So why did we get lines in the spectroscope?

• Niels Bohr (1885 1962)
• Worked with Rutherford
• Model of the hydrogen atom the single electron
  of the hydrogen atom can circle the nucleus only
  in allowed paths called orbits
• Lowest energy closest orbit to the nucleus

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Bohr model of the atom
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Bohr's Model of the Atom (cont.)

• Bohr suggested that an electron moves around the
  nucleus only in certain allowed circular orbits.

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Bohr's Model of Hydrogen
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Bohr's Model of the Atom (cont.)

• Each orbit was given a number, called the quantum
  number.

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Importance of Bohr Model

• Using charge and mass of an electron and Plancks
  constant (Eh?)
• Calculated the energies that an electron should
  have in the orbits.
• Compare calculationg to the line spectrum
• The calculations were correct
• The energy that Bohr model said an electron
  should have, was the same energy that the colored
  lines produced from the bright line spectrum

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Problem with Bohr Model

• His mathematics only applied to the Hydrogen atom

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Bohr Model of the Atom

• Bohr
• Orbit
• electrons were treated as
• correctly predicted line spectrum for __________,
  but could not for any other element

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What to do now ??

• Bohr treated electrons like particles
• 1924 Louis de Broglie noticed that the spectrum
  lines could be explained by wave properties
• Example waves confined in a space have only
  certain frequencies.

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The Quantum Mechanical Model of the Atom (

• The figure illustrates that electrons orbit the
  nucleus only in whole-number wavelengths.

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The Quantum Mechanical Model of the Atom (cont.)

• The de Broglie equation predicts that all moving
  particles have wave characteristics.

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Heisenberg Uncertainty Principle

• The Heisenberg uncertainty principle states that
  it is fundamentally impossible to know precisely
  both the velocity and position of an electron at
  the same time.
• The only quantity that can be known is the
  probability for an electron to occupy a certain
  region around the nucleus.

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Heisenberg Uncertainty Principle

• To see something, light must hit the object,
  bounce off it, and come back to our eye
• When light hits an electron, it makes it move
  because the electron is so small.
• By the time the reflected light gets back to our
  eye, the electron is no longer where it was.

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The Quantum Mechanical Model of the Atom

• Using de Broglies and Heisenburgs thoughts
• Schrödinger treated electrons as waves in a model
  called the quantum mechanical model of the atom.

• Schrödingers equation applied equally well to
  elements other than hydrogen.

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Erwin Schrödinger, 1926

• Who has worked with the sin and cosine curve?
• Basically, he applied a wave formula (like sin or
  cosine) to the properties of the electrons
• Worked for all atoms
• Create electron orbitals instead of orbits
• Can not pinpoint the location of the electron

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The Quantum Mechanical Model of the Atom

• The wave function predicts a three-dimensional
  region around the nucleus called the atomic
  orbital.

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Orbitals

• Three dimensional region about the nucleus in
  which a particular electron can be located

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Hydrogen Atomic Orbitals (cont.)

• Each energy sublevel relates to orbitals of
  different shape.

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Schrodinger

• Orbitals - Mathematical representations of where
  electrons could be (Not specific)
• Can not ._______________
• Treated electrons as _________

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Result of Schrodinger

• Quantum Theory
• Mathematically describes the wave properties of
  electrons
• Creates orbitals which when added together, look
  like an electron cloud