diapositivas modelo atómico de bohr
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Modelo Atómico deBohr.
FUNDAMENTAL CONCEPTS OF
QUANTUM PHYSICS
F!ic" III. #P $ %'
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Early Models of the Atom
It was known that atoms
were electrically neutral, but
that they could become
charged, implying that there
were positive and negative
charges and that some of
them could be removed.One popular atomic model
was the “plumpudding!
model"
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Early Models of the Atom
#his model had the atom consisting of a bulk
positive charge, with negative electrons buried
throughout.
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Early Models of the Atom
$utherford did an e%periment that showed that
the positively charged nucleus must be
e%tremely small compared to the rest of theatom. &e scattered alpha particles ' helium
nuclei ' from a metal foil and observed the
scattering angle. &e found that some of the
angles were far larger than the plumpudding
model would allow.
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Early Models of the Atom
#he only way to
account for the
large angles was to
assume that all thepositive charge
was contained
within a tiny
volume ' now we
know that the
radius of the
nucleus is ()(****
that of the atom.
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+.(* Early Models of the Atom
#herefore, $utherford-s
model of the atom is mostly
empty space"
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+.(( Atomic pectra" /ey to the tructure
of the Atom
A very thin gas heated in
a discharge tube emits
light only at
characteristic
fre0uencies.
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Atomic pectra" /ey to the tructure of the
Atom
An atomic spectrum is a line spectrum ' only certain
fre0uencies appear. If white light passes through such a
gas, it absorbs at those same fre0uencies.
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Atomic pectra" /ey to the tructure of the
Atom
#he wavelengths of electrons emitted from
hydrogen have a regular pattern"
1+23
#his is called the 4almer series. R is the
$ydberg constant"
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Atomic pectra" /ey to the tructure of the
Atom
Other series include the 5yman series"
And the 6aschen series"
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Atomic pectra" /ey to the tructure of the
Atom
A portion of the complete spectrum of hydrogen
is shown here. #he lines cannot be e%plained by
the $utherford theory.
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#he 4ohr Atom
4ohr proposed that the possible energy states for atomic
electrons were 0uanti7ed ' only certain values were
possible. #hen the spectrum could be e%plained as
transitions from one level to another.
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#he 4ohr Atom
4ohr found that the angular momentum
was 0uanti7ed"
1+((3
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#he 4ohr Atom
An electron is held in orbit by the 8oulomb force"
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#he 4ohr Atom
9sing the 8oulomb force, we can calculate the
radii of the orbits"
1+(+3
1+(:3
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#he 4ohr Atom
#he lowest
energy level iscalled the ground
state; the others
are e%cited
states.
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#he 4ohr Atom
#he correspondence principle applies here as
well ' when the differences between 0uantumlevels are small compared to the energies, they
should be imperceptible.
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