Radioactivity Flashcards
What is meant by the decay constant of an isotope?
The decay constant is the probability of decay of a nucleus per unit time.
What happens to the mass number of a nucleus when it undergoes alpha decay?
-4
What happens to the proton number of a nucleus when it undergoes alpha decay?
-2
What happens to the mass number of a nucleus when it undergoes beta decay?
Nothing
What happens to the proton number of a nucleus when it undergoes beta - decay?
+1
What happens to the proton number of a nucleus when it undergoes beta + decay?
-1
What is an alpha particle?
Two protons two neutrons bound together
What is a beta + particle?
A positron
What is a beta - particle?
An electron
What is gamma radiation?
High frequency photon
What is the penetration depth of alpha particles?
Thin sheet of paper, a few centimetres of air
What is the penetration depth of beta - particles?
1-3 mm of aluminium
What is the penetration depth of beta + particles?
VERY short because they are annihilated by electrons
What is the penetration depth of gamma particles?
Reduced by a few cm of lead
What is produced in an alpha decay?
A single alpha particle.
What is produced in a beta + decay?
A positron and a neutrino
What is produced in a beta - decay?
An electron and an antineutrino
What does random mean, in the context of a decay?
We are unable to predict when a particular nucleus in a substance will decay or which one will decay next.
What does spontaneous mean, in the context of a decay?
The decay of nuclei is not affected by the presence of other nuclei in the substance or external factors.
What is the atomic mass unit?
A 1/12 of the mass of the nucleus of a carbon-12 nucleus.
What is radioactive activity?
The number of decays per unit time
What is the conservation of lepton number?
The total Lepton Number before a nuclear change will equal the total Lepton number after.
What is the conservation of baryon number?
The total Baryon Number before a nuclear change will equal the total Baryon Number after.
What is the binding energy?
The energy required to disassemble the protons and neutrons in a nucleus into their separate parts.
What is a half-life?
The time taken for the activity of a substance to reduced to 50% of its value.
