Radioactivity Part 2 Flashcards
Radioactive Decay – Alpha
Large nucleus
Consists of 2 neutrons and 2 protons to from particle
Is a Helium particle
The element emits Energy and alpha particle to achieve stability
Alpha Decay Equation
Atomic mass (p + n)
Atomic number (p)
To find number of neutrons: atomic mass – protons
= 238 - 92=146
n: 146 n: 144 (lost 2 neutrons)
p: 92 p: 90 (lost 2 protons)
emits 2 protons + 2 neutrons that combine to form Helium
To find a tomic mass
= neutrons + protons
= 144+90=234
How dangerous is Decay
‘Least’ (used advisedly) dangerous of all radioactive particles
Heaviest of all decay process products
Travels a few centimetres through air
Cannot pass through a sheet of paper (0.09 mm) A4 (90GSM) is 5g in weight
Cannot penetrate epidermal tissue but can cause erythema(can burn skin)
If emitted inside the body it can cause organ and tissue damage
Alpha Particles - Clinical Practice
Cancer Treatment
Inserting sources into cancer masses
Alpha emissions destroy cancer cells
Lacks penetrating power so very localised area of effect
Development of Targeted Alpha Particle Therapy for Solid Tumors
Beta Decay
Unstable atom with too many neutrons or protons
Protons and neutrons can transform into each other
Process to enable stability
Occurs at subatomic level of quarks
UP and DOWN quarks carry fractional charge of the electron
Results in the release of an electron
Electrons released from the nucleus are called Beta Particles
Two types
Positron +
Negatron -
Positron Decay +
Problem: Excess Protons
Solution: Protons transform into a Neutron
Result: Nucleus loses a proton however gains a Neutron
Change in Proton count = change in atomic number
Change in atomic number = change of the original element into another one
Positron Decay +
Proton consists of 2 up and 1 down quark
P = U+U+D (2/3)+(2/3)+(-1/3) = 1
Up quark changes to a Down quark
Releases a Positron and a Neutrino
Proton becomes a neutron
N=U+D+D (2/3)+(-1/3)+(-1/3)= 0
Energy is conserved so energy ‘lost’ = 1
Released as Positive Electron / Positron/ +
Remember:
p= UUD
n=UDD
Positron = +
Neutrino = energy particle (v)
Positron Decay +
Problem: too many protons
Solution: transform Proton into a Neutron
Result: Mass stays the same - + plus energy
Transforms into a different element
Negatron Decay -
Problem: Excess Neutrons
Solution: Neutron transform into a Proton
Result: Nucleus loses a neutron however gains a proton
Release of - Beta Minus
Change in Proton count = change in atomic number
Change in atomic number = change of the original element into another one
Negatron Decay -
Problem: Excess Neutrons
Solution: Neutron transform into a Proton
Result: Nucleus loses a neutron however gains a proton
Release of - Beta Minus
Change in Proton count = change in atomic number
Change in atomic number = change of the original element into another one
Negatron Decay -
Neutron consists of 1 up and 2 down quark
N= U+D+D (2/3)+(-1/3)+(-1/3) = 0
Down quark changes to an Up quark
Releases a -1 charge
Neutron becomes a proton
P=U+U+D (2/3)+(2/3)+(-1/3)= 1
Energy is conserved so energy ‘gained’ = -1
Released as negative Electron / negatron/ -
Remember:
p= UUD
n=UDD
Positron = +
Negatron = -
Neutrino = +ve energy particle ()
Anti Neutrino = -ve energy particle ()
Positron Decay -
Problem: too many neutrons
Solution: transform neutron into a proton
Result: Mass stays the same - - plus energy
Transforms into a different element
How dangerous is Beta Decay
Can travel up to a metre through air
Passes through a sheet of paper
Can not penetrate a few mm’s of aluminium sheets
Can penetrate skin but not internal organs (external exposure)
Can be more harmful if ingested or inhaled
Clinical use of Beta Decay -
Positron Emission Tomography (PET) Scans
Radionuclide called fluorodeoxyglucouse (FDG) injected
Glucose absorbed faster rate by cancer cells
Beta + decay emissions
Interact with orbital electrons inside body
Annihilation of electron and positron produces gamma rays
Gamma Decay
No particles emitted
High energy gamma ray released
Unstable atom with excess energy
Aims for stable ground state
Atoms remain unchanged
No mass no change just energy
Neutrons and Protons remain unchanged
