Download Bell ringer... 12/3-12/4

12/3-12/4
Bell ringer...
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What is an isotope?
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If a sample contains 1000 atoms of Fe with 91.75% Fe-56,
5.85% Fe-54, and 2.40% Fe-57...
✦
What is the atomic mass for the sample?
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For the most common isotope how many…
✤
p ?
✤
N ?
✤
e?
+
0
-
Isotopes and Radiation
0
+
Ne-16 Ne-19 Ne-20 Ne-20
Problems with atomic
structure...
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Why don’t e- get pulled into the nucleus?
Why don’t p+ blow the nucleus apart?
Similar systems...
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How does these questions compare to our
solar system?
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Why don’t the planets get pulled in to the
sun?
Why doesn’t the sun blow up?
Similar systems...
Large and small
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Planets don’t get pulled into the sun due to a
balance between the outward force of their
momentum acting agains the suns gravity
e- likewise have outward momentum acting in
contrast to the inward pull of their charge
attraction
Large and small
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The nucleus of the atom is held together by
what is known as “Strong Force”
Strong Force
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Strong force is a powerful interactive force
0
between the nucleons (p+ & n )
Strong force only acts over very short
distances (about the diameter of a p+)
Based on gluons, pions, and quarks...
What are gluons, pions, and
quarks?
Don’t ASK!!!
Breaking Strong Force
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Strong force can be overcome...
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If the nuclei of atoms become too large
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Atomic number over 83
If the nuclei has too many or too few n
to p+
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What happens then?
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If strong force is overcome the nucleus
begins to break…
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This is radiation!
Radiation comes in three primary forms
Radiation
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Alpha radiation (α)
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Composed of a particle with 2p+ and 2 n
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Beta radiation (β)
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Two forms electron emission (ß-) and
positron emission (ß+)
ß radiation
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Electron emission (ß-)
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Splits a n into a p+ and e0
Positron emission (ß+)
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Splits a p+ into a n0 and positron (e+)
Summary of radiation
Emission
(leaving atom)
α
4
2
α
4
or 2
He
Change in atomic
Change in mass
#
-4amu
-2p+
+1p+
-1p+
β-
e-
0
(no change)
β+
positron
(nope)
0
(no change)
Gamma radiation!
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Has a ray nature (no particle is emitted)
Does not significantly change mass or charge
of nuclei
Is represented with an * (Cs-137*)!
Radiation
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U-238
C-14
O-15