Modern Physics
Radioactive Decay
Radioactive Decay
Look at the periodic table given to you.
Find element with the atomic number 6
What is it?
Radioactive Decay
The element with the atomic number 6 is Carbon
Look at the atomic mass below the word Carbon
What is it?
Radioactive Decay
The mass is 12.011 amu. Remember that
protons and neutrons are about 1 amu each
Therefore you can
assume that there
are 12 particles in
the nucleus,
6 protons
6 neutrons
Radioactive Decay
You would then write the nuclear symbol for
Carbon – 12 as 126C (with the 6 over the 6)
Radioactive Decay
Find Oxygen on the chart.
Radioactive Decay
Find Oxygen on the chart.
Atomic number 8. How many protons does
oxygen have?
Radioactive Decay
Find Oxygen on the chart.
Atomic number 8. How many protons does
oxygen have?
Yes – 8 protons
How many neutrons
does the most
common Isotope of
Oxygen have?
Radioactive Decay
Find Oxygen on the chart.
Atomic number 8. How many protons does
oxygen have?
Yes – 8 protons
How many neutrons
does the most
common Isotope of
Oxygen have? 8
Radioactive Decay
Find Argon on the chart. Number 18
Radioactive Decay
Find Argon on the chart. Number 18
How many protons does it have?
Radioactive Decay
Find Argon on the chart. Number 18…
How many protons does it have? 18
I think you
are getting it.
How many total
Protons and
Neutrons?
Radioactive Decay
Find Argon on the chart. Number 18…
How many protons does it have? 18
I think you
are getting it.
How many total
Protons and
Neutrons?
40
Radioactive Decay
• Write the symbols for the following atoms
most common isotope.
• Fluorine(9)
• Neon(10)
• Sodium(11)
• Radon(86)
• Uranium(92)
Radioactive Decay
• Review from yesterday
• An atom is stable (not radioactive) if it is in the
belt of stability
• An atom is unstable (radioactive) if it is
outside the belt of stability
• All elements beyond number 83, Bismuth are
unstable - WHY?
Radioactive Decay
• Above element 83, the protons are farther
and farther away from each other in the
nucleus, therefore requiring a greater nuclear
force to overcome the electrostatic repulsive
forces. The nuclear force is not strong enough
to hold together the protons when more than
83 of them are packed into a nucleus.
Radioactive Decay
• Three types of radioactive decay
•
4α
2
•
0
-1
•
0
+1
alpha particle decay also shown as 24He
ß Beta particle decay (An electron from a neutron)
ß Positron emission (a positively charged electron)
• ϒ gamma ray High energy electromagnetic
waves
Radioactive Decay
•
4α
2
alpha particle decay also shown as 24He
An alpha particle is two protons and two
neutrons bound together and emitted from the
nucleus. Alpha particle are identical to a helium
nuclei and have a charge of 2+
Radioactive Decay
•
0
1
Beta
particle
decay
ß
• A beta particle is actually an electron emitted
from the nucleus. To create a beta particle, a
neutron converts itself into a proton and
ejects the right combination of quarks to make
an electron
Radioactive Decay
•
0
+1
Positron
emission
ß
• Elements below the belt of stability have too
many protons. To decrease the number of
protons, a proton emits a positron, or
positively charged electron
Radioactive Decay
• Not a decay per say, but another way to get
rid of too many protons, is Electron Capture
• In electron capture, an inner orbital electron is
captured by the nucleus of its own atom. This
electron combines with a proton and forms a
neutron.
Radioactive Decay
Radioactive Decay