Bohr Model

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Bohr Model
I. Explanation for the spectral lines
When atoms are excited by heat or electricity,
they release light energy This light can be
broken into specific wavelengths of light by a
prism Each element gives off its own LINE SPECTRUM
First noticed with hydrogen
Gave off 4 bands of visible light
A. Balmer
Noticed a mathematical relationship between the
wavelengths
Later, spectral lines found in the IR and UV
range, which followed the relationship
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Rydberg Equation
RH Rydberg constant n1 and n2 positive integers
Wont calculate with this, but know why it is
important
Where do n1 and n2 come from?
B. Neils Bohr
Believed it was due to arrangement of electrons
Accepted the Rutherford model of atom
Assumed that electrons existed in specific areas
orbitals
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Bohrs Theory

• Electrons exist in specific orbitals, defined by
  how much energy they have.
• More energy, further away from nucleus
• 2. Energy in orbits have specific amounts of
  energy
• Energy is not lost as electrons move
• 3. Energy can be gained as electrons move to
  higher energy levels, or lost as they drop to
  lower levels
• Energy of an electron in a particular level is
• En -2.178 x 10-18
• n2

joule
The n1 and n2 from the Rydberg equation refer to
the orbits of the electrons
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II. Energy diagram of Hydrogen Atom
Energies are listed as negative
More energy, further away
n1 is closest orbit, most stable least
energy e- can gain energy and jump up to higher
levels n ? Electron has jumped off Energy of
e- is zero Zero state
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• To calculate the energy lost or gained from an
  electron jump in hydrogen
• Use the energy formula to determine the joules of
  energy in the starting and ending level.
• b. Subtract the starting level from the final
  level
• (Negative answer means you are losing energy as
  light, positive means you are gaining potential
  energy)

En -2.79 x 10-18 J
n2
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III. Uncertainty in Atoms
As we said before, matter can act as a wave,
especially small, fast moving particles Since a
wave exists out in space, we cant say it has an
exact position. Heisenbergs Uncertainty
Principle The more precisely we know an
electrons momentum, the less precisely we know
its position. (we cant know where an electron
is and where its going) We now describe the
location of electrons in terms of probable
locations