4: Atoms and Radiation Flashcards
What is radioactive decay?
Some atomic nuclei are unstable. The nucleus gives out radiation as it changes to become more stable. This is a random process called radioactive decay.
What are the four ways an atom may emit nuclear radiation?
- an alpha particle (α) - This consists of two neutrons and two protons, it is the same as a helium neucleus.
- a beta particle (β) - a high speed electron ejected from the nucleus as a neutron turns into a proton.
- a gamma ray (γ) - electromagnetic radiation from the nucleus.
- a neutron (n).
What is half-life?
The half-life of a radioactive isotope is the time it takes for the number of nuclei of the isotope in a sample to halve, or the time it takes for the count rate (or activity) from a sample containing the isotope to fall to half its initial level.
What is radioactive contamination?
Radioactive contamination is the unwanted presence of materials containing radioactive atoms on other materials. The hazard from contamination is due to the decay of the contaminating atoms. The type of radiation affects the level of the hazard.
What is irradiation?
Irradiation is the process of exposing an object to nuclear radiation. The irradiated object does not become radioactive.
How does the electron arrangements in an atom relate to the emission/absorption of electromagnetic radiation.
When electromagnetic energy is absorbed by an atom, the electron arrangements may change by moving to a higher energy level, further from the nucleus.
When electromagnetic energy is emitted, the electron arrangements may change by moving to a lower energy level, closer to the nucleus.
How are nuclear equations used to represent radioactive decay?
In a nuclear equation, an alpha particle is represented as: 4 2 He
A beta particle is represented as: 0 -1 e
The emission of different types of nuclear radiation may cause a change in the mass and / or the charge of the nucleus. For example:
219 86 radon ———>215 84 polonium + 4 2 He
Alpha decay causes both the mass and the charge of the nucleus to decrease
14 6 carbon ———>14 7 nitrogen + 0 -1 e
Beta decay does not cause the mass of the nucleus to change but does cause the charge of the nucleus to increase.
The emission of a gamma ray does not cause the mass or the charge of the nucleus to change
Required Practical Activity 21: What apparatus is required to investigate the amount of infrared radiation from different surfaces?
- a Leslie cube
- a kettle
- an infrared detector
- a heatproof mat
Required Practical Activity 21: State a method you could use to investigate the amount of infrared radiation radiated from different surfaces.
1: Put the Leslie cube onto the heatproof mat.
2: Fill the cube with very hot water an put the lid on the cube.
3: Use the detector to measure the amount of infrared radiation from each surface. Make sure that the detector is the same distance from each surface.
