2. Beta Decay
Type of Radioactive Decay
• Negative charge
• An electron
• Result
att end
R
lt off beta
b t decay
d
d off reaction
ti the
th
nuclides’:
– Mass
M
# remains
i the
h same
– Atomic number increases by 1
• http://www
http://www.ndt
ndted.org/EducationResources/HighSchool/R
adiography/Graphics/Flash/transmut swf
adiography/Graphics/Flash/transmut.swf
3. Positron emission
Type of Radioactive Decay
• + charge
g
• Has mass of electron
• Result of positron emission at end of
reaction the nuclides’:
– Atomic number decreases by 1
– Mass stays the same
• Positron emission converts a proton to a
neutron
4. Gamma Radiation
Type of Radioactive Decay
• High energy waves emitted from a nucleus
as it changes from the excited state to the
ground state
state.
• No Change in the Nucleus!
Deflection of Decay Particles
• Opposite charges attract each other
other.
• Like charges repel each other.
• http://www
http://www.ndt
ndted.org/EducationResources/HighSchool/R
adiography/Graphics/Flash/transmut swf
adiography/Graphics/Flash/transmut.swf
• http://www
http://www.mhhe.com/physsci/chemistry/e
mhhe com/physsci/chemistry/e
ssentialchemistry/flash/radioa7.swf
• Nuclear decay
Summary of the most common
forms of radiation
Particle
Mass
Charge
g Symbol
ym
Penetrating
g
power
Alpha
4 amu
+2
Low
Beta
0 amu
-1
Moderate
Positron
0 amu
+1
Moderate
G
Gamma
0 amu
N
None
hi h
high
Table O
Half Life=
time it takes for ½ the atoms in the radioactive
sample to decay into a different substance.
Half-life Concept
Half-Life
• Decay of 20.0 mg of 15O. What remains
after 3 half-lives?
half lives? After 5 half-lives?
half lives?
• See Table N
Selected
Radioisotopes
• To find the amount of a sample remaining
after a certain amount of days:
• 1. Find the half-life on Table N.
• 2. Make a table with 2 columns: time and
mass
• 3. Begin your table with zero time.
How much of a 100 gram sample of iodine131 will
ill remain
i after
ft 24 d
days?
?
TIME
MASS
0 days
100 g
8 days
50 g
16 days
25 g
24 days
12.5 g
Phosphorous-32 has a half life of 14.3 days.
Determine how many half-lives elapse during 57.2 days.
How many milligrams remain if you start with 4.0mg?
Time
Mass
The half life of radon-22 is 3.824 days.
Aft what
After
h t time
ti
will
ill one-fourth
f
th of
f a given
i
amountt of
f radon
d
remain?
Time
Mass
A sample contains 16 mg of polonium-218. After 12 minutes, the sample will
contain 1.0 mg of polonium-218. What is the half life of polonium-218?
Time
m
Mass
The half life of I-123 is 13 hr.
hr How much
of a 64 mg sample of I-123 is left after 39
hours?