Topic 4-Atomic structure Flashcards
Who did the alpha scattering experiment?
Rutherford.
What happened in the alpha scattering experiment?
Positive alpha particles were fired at thin particles in a gold sheet.
What were the results of the alpha particle scattering experiment?
Most particles passed straight through but others were deflected slightly.
What did the deflecting alpha particles show?
That atoms must have a positive nucleus.
What did the alpha particles passing through show?
That most of the atom must be empty space.
What is the radius of an atom?
1 x 10 to the power of minus 10 m.
What are isotopes?
Different forms of the same element.
What are the three types of radiation?
- Alpha.
- Beta.
- Gamma.
What is ionising radiation?
Radiation that knocks electrons off other atoms, creating positive ions.
What is the ionising power of radiation?
How easily ionising radiation knocks electrons off.
What is alpha radiation?
When an alpha particle is emitted from the nucleus of a particle.
Are alpha particles strongly ionising or weakly ionising?
Strongly ionising.
Give two characteristics of alpha particles.
- They don’t penetrate very far into materials.
- Strongly ionising.
Give a use of alpha particles.
Smoke detectors.
What are beta particles?
Fast moving electrons released by the nucleus of a particle.
Give two characteristics of beta particles.
- Moderately ionising.
- Penetrate moderately far into materials.
For every beta particle emitted…
A neutron in the nucleus has turned into a proton.
What are gamma rays?
Waves of electromagnetic radiation related by the nucleus.
How far do gamma rays travel through materials?
They penetrate far into materials without being stopped.
Are gamma particles weakly ionising or strongly ionising?
Weakly ionising.
What can absorb gamma particles?
Thick sheets of lead or metres of concrete.
What can absorb beta particles?
A sheet of aluminium.
What can absorb alpha particles?
A sheet of paper.
What do nuclear equations show?
Radioactive decay.
What is the main rule for nuclear equations?
The mass and atomic numbers must be the same on both sides.
What are alpha particles made up of?
Two protons and two neutrons.
What happens when an atom emits an alpha particle in a nuclear equation?
Its atomic number reduces by 2 and its mass number reduces by 4.
How does alpha decay change the mass of the nucleus?
It decreases it.
How does beta decay change the charge of the nucleus?
It increases it.
How do gamma rays change the charge or the mass of the nucleus?
It doesn’t change the charge or the mass.
What can radiation be measured with?
A geiger-muller tuber and counter.
What is activity measured in?
Becquerels (Bq)
What is an issue with trying to measure radioactivity?
The activity never reaches zero.
What is half life?
The time taken for the number of radioactive nuclei in an isotope to halve.
What does a short half life mean?
The activity falls quickly.
What is background radiation?
Radiation that is around us all the time.
What is radiation from space known as?
Cosmic rays.
Why is radiation dangerous?
It can enter living cells and ionise atoms and molecules within them, leading to tissue damage.
What disease can radiation cause?
Cancer.
What is nuclear fission?
A type of nuclear reaction that is used to release energy from large and unstable atoms by splitting them into smaller atoms.
What is nuclear fusion?
Fusing atoms together.
Does nuclear fusion give out more energy than nuclear fission?
Yes.
Does nuclear fusion or fission give out more energy?
Fusion does.
What is a disadvantage to nuclear fusion?
It is expensive.
Why is nuclear fusion expensive?
The temperature and pressure needed is very high.
What is a disadvantage to nuclear fission?
The risk of explosion.
