Transcript Radioactive Decay

Radioactive Decay
Read pages 191-196
157
Atoms are held together by
THE
STRONG NUCLEAR FORCE
There are different types of
nuclear radiation
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Alpha particles
Beta particles
Gamma rays
Neutron emission
Alpha particles
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Positively charged
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More massive than other
types
A helium nucleus
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, which carries a charge of
.
Released in the
disintegration of radioactive
elements
Consists of two protons
and two neutrons
http://library.thinkquest.org/3471/radiation_types_body.html
Beta particle

A charged electron
emitted during certain
types of radioactive
decay
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Neutrons decay to
form a proton and a
high speed
electron
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The electron is ejected
Neutron emission
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is a type of
radioactive decay of
atoms containing
excess neutrons, in
which a neutron is
simply ejected from
the nucleus.
Gamma rays

High energy photon emitted by a nucleus
during fission and radioactive decay
What stops it?
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Alpha
Beta
Gamma
Isotope
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An atom with a different number of
neutrons is called an isotope
Hydrogen usually is a proton and an
electron
If it has a neutron it is considered an
isotope
Hydrogen
deuterium
0 neutrons 1 neutron
tritium
2 neutrons
Half-lives
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The rate of decay of an isotope is called the halflife.
A half life is the amount of time it takes for half
of the amount to decay.
It is constant
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Different elements have different half-lives
Radium-226=1620 years
Uranium-238 = 4.5 billion years
158
200g radium -226
1620years
half-life of
100g
1620
50g
3240
_____g
4860
12.5g
_______
6.25g
8100
________g
9720
Table Design
Half life
1
2
3
4
5
Amount
remaining
Time Past
Periodic Table Practice
mass
Lithium
7 Mass=p + n
Atomic
symbol
Atomic
number
3
3P
4N
Li
Neutrons = mass - protons
REMEMBER—
this is all about isotopes
Atomic number = # of protons
 You absolutely must figure your own
mass or number of neutrons
 Don’t use the chart
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Mass = protons + neutrons
 Neutrons = Mass – protons
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Radiation in Everyday Life