Chapter 4: Atomic structure
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- Created by: Skidmore
- Created on: 12-07-17 16:14
What is the radius of an atom?
1 x 10(-10) metres
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What is the radius of a nucleus compared to the radius of an atom?
less than 1/10 000 of the radius of an atom
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Where is most of the mass of an atom concentrated to?
Most of the mass of an atom is concentrated in the nucleus
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What subatomic particles make up an atom?
Protons, Neutrons and Electrons
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Why are the electrons arranged at different distances from the nucleus?
They have different energy levels
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How might the arrangement of the electrons be changed?
With the absorption of electromagnetic radiation (move further from the nucleus; a higher energy level) or by the emission of electromagnetic radiation (move closer to the nucleus; a lower energy level).
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In an atom, the number of electrons is equal to the number of protons in the nucleus. True or False?
True
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What charge do atoms have?
None
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All atoms of a particular element have the same number of protons. True or False?
True
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What is the name for the number of protons?
Atomic number
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For an atom to be an isotope, it needs to have a) more/less electrons b) more/less protons c) more/less neutrons?
C
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What was the first model of an atom and who created it?
Plum pudding, J.J Thompson
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What did this model show?
The atom is a ball of positive charge with negative electrons embedded in it
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What was the name of the second model and who created it?
Nuclear model, Ernest Rutherford
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How did they come up with this model? (Hint- scattering experiment)
They aimed a beam of alpha particles at a thin foil of metal and according to Thomson's model, they should all pass straight through. But some of the alpha particles bounced off the foil in all directions.
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What was their overall conclusion?
That the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged
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What do unstable nuclei give out and when?
Radiation as it changes to become more stable
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What is the name for this?
Radioactive decay
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Is this process random or no?
Yes it is random
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What is activity?
Activity is the rate at which a source of unstable nuclei decays
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What is activity measured in?
Activity is measured in becquerel (Bq)
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What is a count-rate?
Count-rate is the number of decays recorded each second by a detector
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What are the 3 types of decay?
Alpha, Beta and Gamma
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Describe alpha decay?
An alpha particle is emitted. This consists of two neutrons and two protons, it is the same as a helium nucleus.
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What happens to the atomic number and mass number of the element?
The nucleus has two fewer protons, so the atomic number decreases by two. The nucleus also has two fewer neutrons, so the mass number decreases by four. A new element is formed.
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What material can stop alpha decay?
Paper
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How ionising is it?
The most ionising
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What is the range in air for alpha decya?
A few centimetres. Shortest.
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Give an item where alpha decya is used?
Smoke alarms
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Describe beta decay?
A neutron turns into a proton. Therefore, a high speed electron is ejected from the nucleus.
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What happens to the atomic number and mass number of the element?
The nucleus has one more proton, so the atomic number increases by one. The nucleus has one less neutron, but the mass number is unchanged. A new element is formed.
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What material can stop beta decay?
Aluminium
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How ionising is it?
Moderate. Middle.
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What is the range in air for beta decay?
15cm. Moderate/medium range.
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Give an item where beta decay is used?
Beta radiation is used for tracers and monitoring the thickness of materials
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Describe gamma decay?
These are very high-energy electromagnetic waves. They have no charge and no mass.
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What happens to the atomic number and mass number of the element?
The emission of a gamma ray does not cause the mass or the charge of the nucleus to change
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What material can stop gamma decay?
Centimetres of lead or metres of concrete
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How ionising is it?
Least ionising
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What is the range in air for gamma decay?
Many metres
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Give a use where gamma decay is used?
Killing cancer cells
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What are nuclear equations used for?
Nuclear equations are used to represent radioactive decay
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SEE SHEET FOR NUCLEAR EQUATIONS!!!
SEE SHEET FOR NUCLEAR EQUATIONS!!!
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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.
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How to work out half life?
Use a graph and see the time it took to half it's original count. You should calculate the average of the values e.g 80 to 40, 40 to 20, 20 to 10.....
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What is radioactive contamination?
Radioactive contamination is the unwanted presence of materials containing radioactive atoms on other materials
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When does radioactive contamination?
Contamination occurs when people swallow or breathe in radioactive materials
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What is irradiation?
Irradiation is the process of exposing an object to nuclear radiation. The irradiated object does not become radioactive.
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Name of use of irradiation?
Irradiating food to kill organisms
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Can irradiation be dangerous and why?
Yes because it can cause mutations in the DNA which can cause cancer
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What is background radiation?
Radiation that is around us all the time
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Give an example of background radiation?
Radon gas
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What is radiation dose measured in?
sieverts (Sv) --- 1000 millisieverts (mSv) = 1 sievert (Sv)
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What is nuclear radiation used for in medicine?
1) Exploration with internal organs and bones 2) Destroying cancerous cells
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Benefits of nuclear radiation...
1) Explore internal organs 2) Treating cancer
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Risks of nuclear radiation...
1) May damage healthy cells causing more cancer 2) High radiation doses are dangerous
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What is nuclear fission?
Nuclear fission is the splitting of a large and unstable nuclei (eg uranium or plutonium) and releases a lot of energy
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What subatomic particle gets absorbed?
A neutron
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What happens when the neutron is absorbed?
The nucleus undergoing fission splits into two smaller nuclei, roughly equal in size, and emits two or three neutrons plus gamma rays. Energy is released by the fission reaction. This creates a chain reaction.
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Give an example of uncontrolled nuclear fission?
A nuclear bomb
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What is nuclear fusion?
Nuclear fusion is the joining of two light nuclei to form a heavier nucleus. In this process some of the mass may be converted into the energy of radiation
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What energy type and quantity does it cause?
Huge amounts of thermal energy
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Why can't we use it as an energy source?
It cannot be used as an energy source yet as it involves extreme temperatures
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Other cards in this set
Card 2
Front
What is the radius of a nucleus compared to the radius of an atom?
Back
less than 1/10 000 of the radius of an atom
Card 3
Front
Where is most of the mass of an atom concentrated to?
Back
Card 4
Front
What subatomic particles make up an atom?
Back
Card 5
Front
Why are the electrons arranged at different distances from the nucleus?
Back
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