Is it possible to turn copper into gold? Discuss with the person next
to you!
Te Whāinga Ako
Describe the three forms of radioactivity – Alpha,
Beta and Gamma radiation.
Pātai: What is a nuclear
reaction?
It is not a physical reaction
It is not a chemical reaction
It is a reaction where there is a change or
rearrangement of the nucleons in a nucleus
Three Types of Nuclear
Reactions
Radioactive decay (alpha, beta, gamma
emission)
Fusion reaction
Fission reaction
Radioactive Decay
Pātai: But why?
Whakatika: There is an
electrostatic force pushing the nucleons apart, but the strong nuclear
force is holding them together. When the electrostatic force overpowers
the strong nuclear force, the atom breaks apart –> radioactive
decay!
This occurs because as the nucleus gets bigger, the
strong nuclear force has to act over a larger volume and therefore
exerts a weaker force!
Some principles apply!
conservation of energy
conservation of momentum (linear and angular)
conservation of charge
conservation of nucleon number
Polonium-211
Polonium-211 is an unstable isotope and goes through alpha
decay to become a more stable lead-207 isotope. It does this by
emitting an alpha particle and energy.
Alpha Particle
Alpha Radiation
Helium nuclei (positively charged), symbol \(\alpha\)
Made up of two protons and two neutrons
Slow moving (up to 10% speed of light)
Short range (up to a few cm)
Least penetration ability (stopped by a sheet of
paper)
Greatest ionizing ability (causes serious harm on
impact/ingestion)
Hydrogen-3
Hydrogen-3 goes through beta decay to become a more stable helium-3
atom. It does this by emitting beta particles.
Akoranga 5 Mahi Tuatahi
Write the date in your books
Try and remember, without using your books, what
are three things that are conserved during radioactive
decay?
Te Whāinga Ako
Describe the three forms of radioactivity – Alpha,
Beta and Gamma radiation.
Beta Radiation
High-energy electron (negative charge), symbol
\(\beta\)
When emitted, a neutron decays (changes) into a
proton inside the nucleus
Can travel up to 90% the speed of light
Medium range: about 30cm
Medium penetration: can be stopped by a sheet of
aluminium about 5mm thick
Gamma Radiation
Symbol \(\gamma\)
Electromagnetic radiation with very high
energy
Occurs as a result of a nucleus being left in a
very excited state after undergoing other types of radioactivity
Fast moving, travels at the speed of light
Has greatest penetration ability: can penetrate
through several centimeters of lead
Has the least ionizing ability
What would happen to each radiation type as it enters a magnetic
field (coming out of the page) traveling from the left?
Pātai: What
is nuclear radiation/materials used for?
Nuclear Reactors
Our current nuclear power reactors utilise nuclear fission of
plutonium to create energy. Unfortunately they also produce radioactive
by-products which are hard to dispose of in a safe way.
Steralisation
It can also be used to steralise a variety of medical instruments and
food.
It can also be used in medical imaging and tracers to follow the path
of materials through an ecosystem.
Smoke Detectors
Inside an ionisation chamber, americium-241 decays through alpha
decay. The alpha particles collide with the air molecules causing them
to become ionized. Because they are now charged, current can be carried
between the two plates inside the chamber.
