Transcript Facts about the Nucleus

Monday, May 5, 2008
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Collect Test Make-Up Packets
Pass back Tests
Begin Chapter 19
Homework – Chapter 3, Page 89
#28, 29, 30
Radioactivity
and
Nuclear Energy
Chapter 19
Importance of the
Nucleus
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Chemical properties are determined by
the number and arrangement of
electrons
Nucleus does NOT strongly affect the
behavior of an atom
BUT the nucleus is very important
Uses of nucleus
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Detecting explosives in luggage
Generation of electric power
Determining the ages ancient items
All these use nuclear processes
Facts about the Nucleus
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Size
Very small
Radius typically 10-13cm
1/100,000 the size of a typical atom
If the nucleus of a H atom were the
size of a ping pong ball, its electron
would be about 0.5km (0.3) miles
away
Facts about the Nucleus
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Density
1.6 x 1014g/cm3
If the nucleus were the size of a ping
pong ball, it would have a mass of 2.5
billion tons
Facts about the Nucleus
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Energy
Nucleus held together very well
Energy in nuclear processes typically
millions of times larger than normal
chemical reactions
Facts about the Nucleus
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Composed of nucleons: neutrons and
protons
Number of protons is atomic number (Z)
– Located at the lower left of element
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Sum of the numbers of neutrons and
protons is mass number (A)
– Located at the upper left of element
Nuclide Symbol
A
Z
14
6
C
P=?
X
N=?
Mass # ?
Atomic # ?
Isotopes and Nuclides
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Isotopes: atoms that have identical
atomic numbers but different mass
numbers
Nuclide: general term applied to each
unique atom
Isotopes and Nuclides
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Example: the following nuclides are
considered isotopes of each other
Carbon-12, carbon-13, and carbon-14
12
6
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C
13
6
C
14
6
C
All have six protons (Z=6), and they have
6, 7, and 8 neutrons
Radioactivity
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EMR – energy that has wave-like behavior
and travels at the speed of light
Radioactivity – the result of the
spontaneous decomposition of a nucleus.
This may include high energy EMR and high
energy particles
14
6
C N e
14
7
0
-1
Radioactive Isotopes
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85% of the 2000 known isotopes
are radioactive.
279 are not radioactive
% abundance is much, much
smaller.
C-12 – 99% of all C
C-14 < 0.1%