P7 Radioactivity Flashcards
What are the three types of radiation?
- Alpha
- Beta
- Gamma
What is an isotope?
Atoms of the same element with the same number of protons but a different number of neutrons
What is the relative mass of an alpha particle?
4
What is the relative charge of an alpha particle?
+2
What is an alpha particle made up of?
Two protons and two neutrons, it is identical to a helium nucleus
How does the nucleus of an atom change when an alpha particle is emitted?
- Its atomic number goes down by 2, and its mass number goes down by 4
- The mass and the charge of the nucleus are both reduced
What is a beta particle?
An electron created and emitted by a nucleus that has too many neutrons compared with its protons
What is the relative mass of a beta particle?
Effectively zero
What is the relative charge of a beta particle?
-1
How does the nucleus of an atom change when a beta particle is emitted?
- A neutron in the nucleus changes into a proton
- The atomic number of the nucleus goes up by 1, and its mass number is unchanged
- The charge of the nucleus is increased, the mass of the nucleus is unchanged
What is activity?
The rate at which a source of unstable nuclei decays
What is activity measured in?
Becquerel (Bq)
What is count-rate?
The number of decays recorded each second by a detector
What is a gamma ray?
Electromagnetic radiation from the nucleus
What is the charge of a gamma ray?
Uncharged
What is the mass of a gamma ray?
No mass
How does the nucleus of an atom change when a gamma ray is emitted?
- No change in the number of protons or neutrons in a nucleus
- So the mass and the charge of the nucleus are both unchanged
What causes neutron emission of a substance?
- Neutrons are emitted by some radioactive substances as a result of alpha particles colliding with unstable nuclei in the substance
- Such a collision causes the unstable nuclei to become even more unstable and emit a neutron
Which is the most penetrating type of radiation?
Gamma
Which is the least penetrating type of radiation?
Alpha
What stops alpha radiation?
Paper
What stops beta radiation?
Aluminium
What stops gamma radiation?
Lead