Radioactivity Flashcards
What is an alpha particle?
Two protons and two neutrons - a helium nucleus.
What does it take to completely absorb an alpha particle?
About 3cm in air or a single sheet of paper.
What does it take to completely absorb a beta particle?
About 1m in air or 1-3mm of aluminium.
What does it take to completely absorb gamma rays?
At least 10cm of solid lead.
What is the background count rate?
The numbers of radioactive decays recorded per second with no source present.
What is the nature of radioactive decay?
It is spontaneous and random.
What is the decay equation for alpha decay?
The parent nucleus decays into an alpha particle and a daughter nucleus, which has a nucleon number 4 lower than the parent and an atomic number 2 lower than the parent.
What is the decay equation for beta- decay?
The parent nucleus decays into an electron, an electron antineutrino and a daughter nucleus, which has the same nucleon number as the parent but an atomic number 1 higher than the parent.
What is the decay equation for beta+ decay?
The parent nucleus decays into a positron, an electron neutrino and a daughter nucleus, which has the same nucleon number as the parent but an atomic number 1 lower than the parent.
Why is nuclear decay random?
It is impossible to predict when a nucleus will decay and each nucleus within the sample has the same chance of decaying per unit time.
Why is nuclear decay spontaneous?
The decay of nuclei is not affected by any external factors such as pressure or the presence of other nuclei in the sample.
What is the half life of an isotope?
The average time it takes for the number of active nuclei in a sample to halve.
What is the activity of an isotope?
The number of radioactive decays per second (measured in Becquerel, Bq).
What is the decay constant of an isotope?
The probability of an individual nucleus decaying per unit time.
What is the half life of carbon-14?
5700 years.
