Topic 2 - Nuclear Decay Flashcards
Background radiation
It’s low levels of radiation cause by nature and man made sources. They are harmless
Becquerel
It’s the unit for radiation or activity which is counts per second
Types of nuclear radiation
Alpha radiation
Beta radiation
Gamma radiation
What happens in a nuclear decay?
The radiation particle emitted will leave the nucleus with a certain amount of KE.
as it travels, it will ionize particles in its path, losing a small amount of that KE at each ionization.
When all KE is transferred, the radiation particle stops and is absorbed by the substance it’s in at that moment
Alpha particles
They’re made up of two protons and two neutrons.
Same as Helium
It’s a relatively large particle with a significant positive charge so it’s highly ionizing.
It loses KE fast so it’s easily absorbed. Can be stopped with paper and skin or even a few centimeters of air
These are most dangerous inside the body. They can cause radiation poisoning, and cancer
But are stopped by skin cells from the outside
Beta particles
a beta particle is an electron emitted at high speed from the nucleus when a neutron decays into a proton
It’s a small size and has a single negative charge so it’s less ionizing than an alpha particle.
Can penetrate much further.
Aluminum sheet is needed to absorb beta particles
Exposure should be minimized both outside and inside the body but no strong danger
Gamma rays
They are high energy, high frequency, electromagnetic radiation.
They have no charge and no mass
They are photons
They rarely interact with particles so they are the least ionizing nuclear radiation.
They’re never completely absorbed but can be reduced by several centimeters of lead or several meters of concrete.
Can cause cancer from long term exposure because they’re very penetrating and weakly ionizing
If there’s a lot of ionization the cells of a human body might die
If there’s less ionization the molecules of the DNA in the cells may change slightly. So cancer
Radioactive decay is spontaneous and random
Spontaneous: we can’t predict when a given nucleus will decay
Random: we can’t predict what nucleus will decay next
Decay constant (lambda)
It’s the probability that the nucleus of an atom will decay.
Activity (A) or (dN/dt)
It’s the number of a sample decaying per second.
A = -(lambda)(N)
The rate of decay of nuclei
The number of nuclei REMAINING in a sample
N = No e^-(lambda)(t)
Half life
The time taken for half of the atoms of that nuclide within a sample to decay
t1/2 = Ln2/lambda
1 atomic mass unit (u) = 1.66x10-27 kg
It’s in the formula sheet
The mass deficit
It’s the difference between the mass of a nucleus and the mass of its nucleons form which it’s made
