Unit 4- Atomic Structure Flashcards
Who discovered the electrons
Jj Thompson
What discovered the atom
John dalton
Who discovered the plum pudding model
Jj Thompson
Who discovered the nuclear model
Rutherford
What are alpha particles
Helium nuclei (2 neutrons and 2 protons)
What are beta particles
Fast moving electron ejected from the nucleus
What are gamma waves
Waves of electromagnetic radiation
What is alpha stopped by
Paper
How is alpha particles used in homes and how does it work
Smoke detectors, ionises air particles causing a current to flow. If there is smoke in the air, it binds to the ions, meaning the current stops and the alarm sounds
Mass and charge of a beta particle
No mass
Charge of -1
Penetration and ionising of an alpha particle
Doesn’t penetrate far
Strongly ionising
Ionising and penetration of beta particle
Moderately ionising
Moderate penetration
What is a beta particle stopped by
Sheet of aluminium
What happens when a beta particle is emitted
A neutron in the nucleus has turned into a proton (atomic number will increase by 1 )
Applications of a beta particle
Used to test thicknesses of sheets of metals, as the particles are not immediately absorbed by the material like alpha radiation would do and it doesn’t penetrate as far as gamma rays.
What is gamma rays stopped by
Thick sheets of lead
What is the penetration and ionising of gamma rays
Penetrate far into materials, weak ionising
What does alpha decay do
Atomic number reduces by 2
Mass number reduces by 4
Charge of the nucleus descreases
What is the mass number
Big number
What is the atomic number
Small number
What does beta decay do
Atomic number increases by 1
What is half life
Time taken for the number of radioactive nuclei in an isotope to halve
Example of a detector that can be used to detect radiation
Geiger- muller tube
Describe mass number in terms of atoms
Total number of protons and neutrons in nucleus
What does gamma decay do
Mass and atomic number does not change
Risks to radiation
High doses can kill cells completely causing vomiting, tiredness and radiation sickness
Lower doses tend to cause minor damage without killing cells. This can increase the mutant cells which divide uncontrollably causing cancer.
What is nuclear fission
Nuclear reaction used to release energy from large unstable atoms (uranium, plutonium) by splitting them into smaller atoms
Process of nuclear fission
- neutron is absorbed
- nucleus splits into smaller nuclei
- releasing energy and gamma rays
- and two or three neutrons
How is the energy produced in fission controlled
Done using control rods which when lowered or raised inside a nuclear reactor, absorb neutrons
Name sources of background radiation
Natural = rocks(granite) cosmic rays(high energy)
Man made = fall out from nuclear weapons testing, nuclear accidents
What is irradiation
Exposure to radiation
What is contamination
Radioactive particles getting onto objects, comes from touching and handling radioactive substances.
What is nuclear fusion
Joining of small nuclei to create a larger heavier nucleus (opposite of fission)
Process of nuclear fusion
- Two light nuclei collide at high speed and join (fuse)
- Create a larger heavier nucleus
- This could be a hydrogen nuclei fusing to produce a helium nuclei
- Some of mass of nuclei is converted into lots of energy
How is radiation used to treat cancer
During radiotherapy, gamma rays are directed carefully to kill the cancer cells without damaging normal cells
What is the unit for the activity of a source
Becquerels
What does a step up transformer do
Increases potential difference and decreases current, therefore reducing thermal energy transfer to surroundings increasing efficiency
What does a step down transformer do
Decreases potential difference so it is at a safer value
What is meant by random nature of radioactive decay
Can’t predict when a nucleus will decay
A negatively charged student touches a tap and receives an electric shock. Why?
Potential difference between student and tap.
Which causes electrons to transfer
Which earths the charge
How to work out count rate
Counts / time in seconds
How to work out activity
Becquerels x mass
One reason why the bananas equivalent dose will help public be more aware of radiations risks
People are able to compare a radiation risk to radiation from bananas
Explain how resistance of filament lamp changes as potential difference increases
- current increases as p.d increases
-which causes temp to increase
-so resistance increases
Why does the alarm switch on when the smoke particles enter the plastic casing
Smoke stops alpha radiation
Why is it safe to use alpha radiation in a house
Doesn’t penetrate very far
Why would a smoke alarm not work with beta or gamma
Beta and gamma will penetrate smoke
So no change in count rate will be detected
Explain ideal properties of a radioactive source for medical diagnosis
-short half life so less damage to cells
- low ionising power so less damage to cells
-high penetration so can be detected outside the body
2 reasons why taking repeat readings could provide more accurate data
- remove anomalies
- calculate a mean
fuels used in nuclear power station
Uranium, plutonium
Why is it dangerous for live wire to touch metal cable
Risk of electric shock
What is the potential difference of the live wire
230 volts
Potential difference of neutral wire
Zero
Potential difference of earth wire
0 volts
Why will a person get an electric shock from the live wire
The potential difference of the live wire is 230 v and the potential difference of the person is 0v therefore there is a large potential difference so charge will pass through their body causing an electric shock
Most appropriate fuse rating for a television/ toaster
3A
When two insulators rub against each other what happens
Electrons pass from one to the other
Radius of atom
1 x 10 to the minus 10
Radius of nucleus
1 x 10 -14
In an atom where is the energy level highest
The further from the nucleus the higher the energy
What is the mass number
Number of protons + number of neutrons
What is the atomic number
Number of protons or electrons
What was the first subatomic particle to be discovered
Electron
What is the plum pudding model
Ball of positive charge with negative electrons embedded in it
Conclusions from alpha scattering experiment
-Most of alpha particles went straight through gold foil therefore atoms are mainly empty space
-some particles were deflected therefore centre of atom much have a positive charge
What did James Chadwick discover
Neutrons
What is radioactive decay
Some isotopes have unstable nucleus so to become stable they give out radiation
What is activity in radioactive decay
The rate at which a source of unstable nuclei decay, measured in Becquerel
What is count rate
Number of decays recorded each second by a detector
Alpha range in air
5cm (low )
Beta range in air
15cm (medium)
Gamma range in air
Several meters (high)
How is gamma used to sterilise medical equipment
-place object in plastic wrapper to stop bacteria entering
-place object near radioactive isotope which emits gamma
-place lead shield in front to protect workers from radiation
Ways to protect against radiation
Alpha = gloves
Beta = lead apron
Gamma = lead apron
Use radiation monitor to measure how much radiation has been received
Dangers of alpha radiation
Strongly ionising but easily stopped by dead cells on skin surface, can be dangerous if inhaled or swallowed
Dangers of beta radiation
Quiet ionising and can penetrate into the body
Dangers of gamma radiation
Weak ionising can penetrate into the body but likely to pass back out again
What is peer review
Scientists review each other’s conclusions from new scientific research. They also check the method used and the accuracy of the results
What affects how much background radiation you receive
Location and occupation
What is the dose of radiation measured in
Sieverts
Conditions for internal organs traced
-Must emit radiation that can pass out of the body and detected
-Tracer must not be strongly ionising to minimise damage to body tissue
-Must have short half life so not present in body for too long
-must not decay into another radioactive isotope
What happens to the neutrons after nuclear fission
They can then be re absorbed by another nuclear nuclei and trigger fission again this is called a chain reaction
