Nuclear Energy
Nuclear Energy
• Nuclear energy is all around us and can be
used for medical purposes.
• Nuclear energy is when an atom is split and
releases energy or particles.
Nuclear Energy
• To fully understand Nuclear Energy we need to
take a look at how an atom can split.
• 1 way this can happen is called
Radioactive Decay.
Radioactive Decay
• Isotopes with unstable nuclei emit particles
and/or energy to become stable isotopes.
• Any time an unstable nucleus emits particles
the number of protons and neutrons changes.
• The energy released is called nuclear
radiation.
Nuclear Radiation
• There are 4 types of nuclear radiation.
Alpha particles
• Alpha particles are actually 2 protons and 2
neutrons. The same as a helium nucleus.
• They are represented by 42He
• Alpha particles are positively charged and
massive.
Beta Particles
• Beta particles are fast moving particles,
usually electrons.
• Because electrons are almost mass less and
have a negative charge we represent Beta
particles as: 0-1e
Positrons
• Once in a while the Beta particle given off
changes its charge to positive.
• This now mass less tiny positive charge is
called a Positron.
• It’s represented by: 0+1e
Gamma Rays
• Gamma rays are not matter they are a form of
electromagnetic energy.
• They are small packets of energy called
photons.
• Although they have no charge, they can excite
atoms and cause chemical reactions.
Neutrons
• Neutron emission is when the atom looses a
neutron.
• It is the hardest to decay to stop. Neutrons do
not have a charge, so the particles are able to
travel through most materials with out
ionizing the material.
• It’s represented by: 10n
Nuclear Decay and Equations
• Nuclear Decay equations are like chemical
reaction equations.
• The nucleus before emitting a particle is the
reactant.
• The particle emitted and the resulting new
isotope are the products.
Nuclear Decay Equations
• When an isotope goes through Beta Decay the
mass number stays the same, but the atomic
number increases by 1.
•
14 C
6
14 N
7
+ 0-1e
• During Beta decay an electron is given off and
a Neutron changes into a proton.
Nuclear Decay and Equations
• When an Isotope goes through Alpha Decay
both the mass number and the atomic
number change.
•
226
88
Ra
222
4 He
Rn
+
86
2
• The reactant has lost 2 protons and 2
neutrons.
Decay Rates
• The time it takes for half of a radioactive
isotope to decay is called a half-life.
Calculating Half Life
• We can use the known half life of each
element to help us figure out how much of a
substance remains.
• Example:
• Radium 226 has a half life of 1599 years. How
long will 7/8ths of a sample take to decay.
• Radium 226 has a half life of 1599 years. How
long will 7/8ths of a sample take to decay.
• Step 1: Figure out how much is left of the
sample at the end of the decay period.
• 1 – 7/8 = 1/8
• Radium 226 has a half life of 1599 years. How
long will 7/8ths of a sample take to decay.
• Step 2: Figure out how many half lives it takes
to get to the sample down to the remaining.
• ½ x ½ x ½ = 1/8
• Radium 226 has a half life of 1599 years. How
long will 7/8ths of a sample take to decay.
• Step 3: Count the number of half lives and
multiply that by the time it takes for one half
life.
• 3 half lives x 1599yrs = 4797 years