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NIELS BOHR´S MODEL OF AN ATOM

In 1913 Niels Bohr proposed a shell model which explained the stable motion of electrons
around the nucleus in discrete orbit
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In this model, the electrons revolve around the nucleus in
defined orbits
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They were discovered by Ernest
Rutherford inside a nucleus
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They were discovered by J
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NEUTRONS: Neutrons are neutrally charged particles
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THE NUCLEUS: The nucleus contains positively and neutrally charged particles called
protons and neutrons respectively

DISCRETE ORBITS: The discrete orbits in which electrons revolve around the nucleus is
called SHELLS
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or in numbers 1, 2, 3…





When the electrons revolve in these discrete orbits or shells, they do not radiate energy and
therefore do not fall into the nucleus
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These
electrons are called Valence Electrons
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This certain number can be obtained by using the following equation: 2n2
where n= the shell number
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ELECTRONIC CONFIGURATION: An atom as a whole is always neutral because the number
of protons and the number of electrons is always equal
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This can be
obtained by knowing the ATOMIC NUMBER or PROTON NUMBER
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• The maximum number of electrons that can be accommodated in the outermost
shell is EIGHT
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ATOMIC NUMBER: The number of protons in an atom
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Number electrons= 20
ATOMIC
MASS


This can also be done written as: 2-8-8-2



PROBLEMS WITH THE MODEL:
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It violates the Heisenberg Uncertainty Principle because it considers
electrons to have both a known radius and orbit
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•

It makes poor predictions regarding the spectra of larger atoms
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•

The Bohr Model does not explain fine structure and hyperfine structure in
spectral lines
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