Chapter 7 - Radioactivity Flashcards
How does a radioactive substance stabilize unstable nuclei?
- It emits radiation.
State the names of the 3 types of radiation.
- Alpha
- Beta
- Gamma
What was the name of the correct model of an atom and who discovered it?
- The Bohr model by Niels Bohr.
State the definition of an isotope.
- Atoms of the same element with same number of protons but different number of neutrons.
How many protons and neutrons are in an isotope of Uranium which has a mass number of 235 and an atomic number of 92?
- Protons = 235
- Neutrons = 143
Describe the characteristics of alpha emission.
- 2 protons and 2 neutrons
- 2+ relative charge
Describe the characteristics of Beta emission.
- It has a charge of -1
- When an unstable nucleus emits beta emission, the atomic number decreases by 1.
Describe the characteristics of gamma emission.
- Electromagnetic radiation
- Uncharged and no mass
- Mass and charge stay the same
Give the 3 materials which can stop the three types of radiation.
Alpha - Paper
Beta - Thin aluminium sheet
Gamma - Thick lead sheet
Identify how far each type of radiation can travel.
Alpha - 5cm
Beta - 1m
Gamma - Unlimited
Why are all radiation types dangerous?
- They can ionise substances they pass through, killing them.
State the definition of the activity of a radioactive source.
- Number of unstable atoms that decay per second.
State the definition of the count rate of a sample.
- Number of counts per second.
What is the half-life of a radioactive isotope?
- Average time taken for the number of nuclei to half.
How do you calculate the count rate after ‘n’ half-lives?
- initial count rate / 2(n)
- n = number of half-lifes
A radioactive isotope has a half-life of 15 hours. A tube has 48 grams of the isotope.
Calculate the mass of the tube after:
- 22.5 hours
- 30 hours
- 18 grams
- 12 grams
What are the 2 factors which decide how effective a radioactive isotope is?
- It’s half-life
- Type of radiation emitted (a,b,y)
Give 2 uses of radioactive isotopes in medicines.
- Medical imaging
- Treatment of cancer
What is nuclear fission?
- Splitting of an atom’s nucleus into 2 smaller nuclei.
How does a chain reaction occur?
- When a fission event causes further fission events.
What is nuclear fusion?
- Forcing 2 nuclei together to form 1 larger nucleus.
What is released when 2 light nuclei collide?
- Lots of energy
Why does a fusion reactor need to be a high temperature?
- This is because the nuclei involved in fusion is difficult to store otherwise.
Give 2 examples where nuclear accidents have occured.
- Chernobyl
- Fukushima
