Radioactivity Flashcards
transmutation
atom changing to another atom type
disintegration
nucleus changes its structure = change in mass number or atomic number
are larger Z more unstable or stable
unstable, as they are larger
more stable =
more neutrons
isotopes
different number of protons same number of neutrons
what are the decay types
positron
k-electron capture
gamma
beta
alpha
how does a nucleus become stable
emitting a particle
energy in the form of a gamma ray
alpha
only ejected if the atomic mass is 150+
occurs when there’s too few neutrons
doesn’t travel far
doesn’t penetrate deep
highly ionising
beta negative
too many neutrons [negatrons: -ve electric charge]
neutron -> potron + e/beta + antineutrino
emission of the beta causes transmutation to a different atom
atomic number increases, mass number stays the same
beta positive
too many protons, an antimatter equivalent to an electron (positron: positive electric charge)
proton -> positron + neutron (remains in nucleus)
positron + electron = annihiliation
positron reacts with the electron releasing two gamma rays (0.51MeV) emitted 180 degrees
beta have a equal mass to an electron
gamma
emitted from the nucleus
wavelength of 10^-8m or less
electron captures
too many protons not enough neutrons, pull an electron in
proton captures an inner electron and converts into a neutron which breaks the unstable nucleus. Nucleus changes from a high to low energy state
excess energy is released as a gamma ray
unstable nucleus emits a beta particle
very penetrating
where do isometric transitions occur
emission of gamma ray = internal conversion
standard definition of activity
activity of preparation:
amount of disintegrations or nuclear transformations occurring in a substance
or number of decays per unit time
definition of activity
number of transformations per second from one gram of radium
half life effective =
physical half life + biological half life
conversions of mCi in Bq
1mCi = 37MBq
1Ci = 37GBq
1Ci = 37,000,000 Bq
what is the average life
amount of time it remains reactive in the nucleus
physical half life
time taken for an element to half its activity
biological half life
may vary dependent on if any abnormal pathology is present, or removal of any material by metabolic or excretory processes
effective half life
time taken for an element in the organ to decay to half its original activity by metabolic process. Depends on the half life of the radioactive decay and the time taken for the radiopharmaceutical to be excreted
what is a therapeutic dose
I-131
what dose do you image and not treat
I-123
short half life
cheap to manufacture
less dose to patients etc
low residual activity
long half life
essential for unsealed sources
