Module 6: Radiation And Health Flashcards
Bound state
An orbital in which the electron is trapped in the electrical potential produced by the nucleus
What does energy quantisation mean?
The total energy of an electron in a bound state can only take on certain values
Ground state
The energy level of an electron with the lowest energy
Electrons will almost always be in their ground state
Excited state
A state with energy higher than the ground state
p = E/c gives the momentum of what?
A photon
Ionisation energy
The amount of energy required to free an electron from an atom
What is ionisation energy determined by? (2)
Nature of the atom
Orbital from which electron originates
Define the electron volt eV
The electrostatic potential energy gained by an electron when it is moved up a potential difference of one volt
r = n^2 aB
What is this formula used for?
To give the allowed radii for electronic orbitals
What is the ground state, E0, of the hydrogen atom?
13.6 eV
What does En = -(Z^2)/n^2 E0 represent?
Is this positive or negative? Why?
The energy of the allowed electronic orbitals
Negative
It takes energy to get the electron unbound
Hydrogen-like atoms
Atoms with one electron (H, He+, Li2+)
In the energy difference between two levels equation, what do n1 and n2 represent?
n1= lower energy level n2= higher energy level
Chemical properties depend entirely on _
Z atomic number
Nucleon
Nuclear constituent (neutron or proton)
Atomic mass of carbon in amu
12 amu
Strong nuclear force
Short range attractive force
Bond protons to protons, neutrons to neutrons, and protons to neutrons
Due to the force between quarks
When is the strong nuclear force overcome? What by?
When the size of the nucleus gets too large
Electrostatic force
What is the difference in mass between the atom and its constituent parts called?
Mass defect
Binding energy
Energy we would need to break the atom into its constituent parts
Which element has the largest amount of energy per nucleon?
Fe iron
Three types of nuclear reaction
Nuclear decay
Nuclear fusion
Nuclear fission
In fusion and fission, the products are ___ stable than the reactants
Why?
More
Energy is released
Nuclear fusion occurs for elements with an atomic number of ____
Smaller than 56
Nuclear fission occurs for elements with an atomic number of _____
Greater than 56
When you break an atom up into its constituent parts, the binding energy converts to ___
Mass
Process by which an unstable nucleus transforms into a more stable nucleus
Nuclear decay
Three types of radiation
Alpha (He nucleus)
Beta (positron or electron)
Gamma rays (photons)
Which type of radiation particle is the largest? Is it also the most harmful?
Alpha
Most can’t get through the skin
Order radiation types by their speed
Gamma (light)
Beta (90% speed of light)
Alpha (10% speed of light)
How does the atomic and mass number of an atom change when it emits an alpha particle?
Mass number -4
Atomic number -2
How does the atomic and mass number of an atom change when it emits a beta particle?
Mass number doesn’t change (electron/ positron mass is extremely small)
Atomic number + or -1
What is emitted in beta- decay?
Electron and anti neutrino
What is emitted in beta+ decay?
Positron and neutrino
Which end of the electromagnetic spectrum do gamma rays occupy?
High end
Very high frequency light
How do the atomic and mass numbers of an atom change when it emits gamma rays?
No change (photons have no charge)
Only state of excitation changes
What does lambda symbolise in radiation formulae?
Decay constant
The larger the decay constant, the ______ the number of radioactive atoms decreases
Faster
What does A symbolise in radiation formulae?
Nuclear activity (rate at which radioactive elements decay)
Bq
Becqueral (unit for nuclear activity)
Describe Bremmstrahlung radiation
Electrons decelerate and emit energy as photons (X-rays)
What is the maximum possible photon energy in an X-ray?
The same as the kinetic energy gained by electrons from the accelerating potential
What is Z-eff?
Z effective (Z-1)
What makes Coolidge tubes better than Crookes tubes in measuring radiation?
The voltage (penetrating ability) and current (beam intensity) are independent of each other
Annihilation
The conversion of mass to energy when a particle and its anti-particles meet (e.g. positron and electron)
A higher energy level of the same type of radiation increases what?
Depth/ range of ionisation
What do collisions involving beta particles result in for those beta particles? Why?
Large changes in their direction and velocity
They are very small and light
Three ways X-rays and gamma rays can interact with matter
Photoelectric effect
Compton scattering
Pair production
Describe the photoelectric effect
Electron absorbs a photon, which gives it enough energy to jump out of its orbit
A free electron and ion are generated
What condition must be met for the photoelectric effect to appear?
The energy of the photon must be larger than the binding energy of the electron
What happens if the photoelectric effect is due to X-rays?
X-ray is absorbed and a photoelectron is expelled
Electron from outer orbital drops into vacant orbital and another X-ray is emitted
Describe the Compton effect
Incoming photon interacts with loosely bound outer electron then leaves with less energy
Electron leaves and atom becomes an ion
Describe pair production
A photon with very high energy can spontaneously convert into an electron-positron pair (energy—> matter)
Free radicals
Molecules which contain unpaired electrons
Very reactive
Can alter important cellular molecules
Deterministic effects of radiation
Early effects
Kills cells
Reduces an organs function
Stochastic effects of radiation
Late effects
Doesn’t kill cells- just damages them
Imperfect repair= mutation
Cause cancer later in life
Absorbed dose
Represents the energy imparted by radiation into material
D=deltaE/deltam
D is absorbed dose
DeltaE is energy lost from beam
Deltam is mass of material which absorbs the radiation
