GCSE REVISION Flashcards
Describe both the plum pudding model and the current nuclear model of the atom.
In the plum pudding model, atoms are spheres of positive charge with tiny negative electrons stuck in them. In the current nuclear model, atoms are made up of a central, positively charged nucleus with negatively charged electrons orbiting around it. This nucleus is made up of protons and neutrons.
Describe what happens when a beam of alpha particles is fired at a thin sheet of gold.
Most of the particles go straight through the sheet, unaffected. Some of the particles are deflected. A tiny number of the particles are deflected back the way they came.
Explain why atoms have no overall charge.
Because the number of electrons (negative charges) in an atom is equal to the number of protons (positive charges) in the nucleus.
What is meant by the ‘atomic number’ of an atom?
The number of protons in the nucleus of that atom.
What process do unstable nuclei undergo in order to become more stable?
Radioactive decay
State the three types of ionising nuclear radiation. Briefly describe what each one is made up of.
Alpha particles — particles consisting of two neutrons and two protons.
Beta particles — fast‑moving electrons.
Gamma rays — waves of electromagnetic radiation.
Which types of ionising radiation aren’t able to penetrate through a sheet of aluminium?
Alpha particles and beta particles
Why does the atomic number of an atom increase by 1 when the atom undergoes beta decay?
Because during beta decay, a neutron in the nucleus turns into a proton, meaning the nucleus has 1 more proton than before.
Define ‘half-life’ in terms of activity.
The time taken for the activity of a sample to fall to half of its initial value.
State two different natural sources of background radiation.
Any two from e.g.:
Unstable isotopes in rocks/building materials.
Cosmic rays.
Unstable isotopes in air.
Unstable isotopes in food.
Give an example of a man‑made source of background radiation.
Any one from e.g.:
Fallout from nuclear explosions.
Nuclear waste.
What is the term for when unwanted radioactive atoms get onto or into an object?
Contamination
When handling radioactive sources, state one safety precaution you could take to lower the risk from irradiation.
Any one from e.g.:
Store radioactive sources in lead‑lined boxes when they’re not being used.
Stand behind barriers that will absorb radiation when using sources.
Explain why contamination can be hazardous.
nswer:
Because contaminating atoms can decay and release radiation which could cause harm.
State and explain whether an alpha or gamma source is more dangerous for a person to be irradiated by.
Gamma source. This is because gamma radiation has a longer range, and so more radiation will reach a person from a gamma source than an alpha source at the same distance. Gamma radiation can also penetrate a person’s body and damage their organs, which alpha radiation cannot.
