P7 Radioactivity Flashcards
Why are radioactive isotopes unstable?
Becuase they have a heavy nucleus
What is nuclear decay?
Radioactive isotopes contain a heavy nucleus so they emitt particles and energy to become stable.
What are the characteristics of Alpha particles?
- Similar to Hellium nucleus (2+ charge)
- Slower than Beta and Gamma
- Lowest penetration (can be stopped by paper)
- Highest Ionisation
What are the characteristics of Beta particles?
- Fast moving electron
- Negative charge
- 1.5x10^8 m/s
- Higher penetration than alpha
- Moderate ionisation
What are the characteristics of Gamma particles?
- EM wave emitted from nucleus
- No charge
- 3x10^8 m/s
- Highest penetration level
- Least ionisation
What can alpha particles be stopped with?
Few centimeters of paper (alpha particles have the lowest penetration)
What can beta particles be stopped with?
1 metre of Aluminium
What can Gamma particles be stopped with?
Several centimeters of lead or 1 metre concrete (highest penetration)
What is the nuclear equation for Alpha decay?
Radioactive element – > Helium + Other element
What is the nuclear equation for Beta decay?
Beta Element — > New element (contains the 1 less protons than the original element) + Electron
What is the nuclear equation for Gamma decay?
Element (with more energy) —> Same element (with less energy)
How can radioactivity be detected?
By using a photographic film or Gieger-Müller tube
What is activity measured in?
Becquerel (Bq)
1Becquerel = 1 decay per second
What is activity?
The number of decays per second.
How do you calculate activity?
Activity = number of decays / time
What is background radiation?
It is a low-level ionising radiation that is produced all the time.
most of this radiation occurs naturally
What are the 4 types of background radiation?
- Radon gas
- Cosmic rays
- Internal radiation
- Man-made factors
How dose radon gas cause background radiation?
Raditation emitted from rocks e.g. granite account for 50% of natural radiation.
How do cosmic rays cause background radiation?
Supernoval explosions in stars cause cosmic rays
What is internal radiaiton?
Radiation caused by radioactive sources present inside our bodies.
What man-made factors cause background radiations?
- Nuclear power stations
- Nuclear testing
- Medicine (gamma rays for radiotherapy)
What is half-life?
The average time taken to reduce the number of radioactive nuclei into a half
How do you calculate the number of nuclei after a specific time?
Final number of nuclei = Original number of nuclei / 2^number of half-lives
What is an alpha particle?
A particle made of 2 protons and 2 neutrons.
(can also be named a helium nucleus)
What is a Beta Particle?
A high speed electron ejected from the nucleus as a neutron turns into a proton
What is gamma decay?
Electromagnetic radiation from the nucleus
What is the nature of an alpha decay?
Particle
What is the nature of a beta decay?
Particle
What is the nature of gamma decay?
Wave
What is the electrical charge of alpha decay?
+2
What is the electrical charge of beta decay?
-1
What is the electrical charge of gamma decay?
0
