P4 atomic structure Flashcards
Structure of atom
Nucleus has protons and neutrons
Electrons surround nucleus in shells
Isotopes
An element that has Same number of protons but different number of neutrons
A
X
Z
A- mass number (nucleons number)
Z- atomic number (proton number)
X- chemical symbol for the element
Neutrons is A-Z
Ionised
Then an atom gains or loses electrons
Energy levels
Electrons occupy the space around the nucleus at a specific distance
Electrons can move levels/shells
Radioisotope
An atom with an unstable nucleus
Activity of radioisotopes
Number of nuclear delays each second
Measured in becquerels (Bq)
1Bq is 1 count per second
Radioactivity
Random process
Not possible to predict when nucleus will decay
Radioactive decay
Produces nuclear radiation- radiation emitted from the nucleus
May be alpha, beta particles or gamma ray or a neutron
Neutron radiation
Release of a high speed neutron from the nucleus, either from the nucleus or a radioactive atom or the result of nuclear fission
Alpha decay
Alpha particle is emitted from nucleus Has helium nucleus 2 protons 2 neutrons Atomic number decreases by 2 Mass number decreases by 4 4 a 2
Beta decay
A neutron decays into proton and electron Electron emitted as beta particle Atomic number increases by 1 Mass number is the same 0 B -1
Gamma decay
Gamma rays emitted from nucleus
Very high electromagnetic waves
No charge or mass
Doesn’t affect mass or charge of nucleus
Background radiation
Ionising radiation that is around us all the time
Background radiation comes from
Natural sources eg. Rocks- granite & cosmic rays from space
Waste products from hospitals
Waste products from nuclear power stations and other industries
X-ray and manufactured radioisotopes used in medical procedures
Small amount from nuclear weapon testing & nuclear accidents
Amount of radiation depends on are you live and job you have
Penetrating power
Alpha has least
Beta
Gamma has the most
Ionising power
Gamma has the least
Beta
Alpha has the most
Half life
The average time it takes for half the nuclei present to decay
Or the time it takes for the activity to fall to half its initial level
Radioactive contamination
The unwanted presence of materials containing radioactive atoms.
Can be on surfaces/within solids,liquids,gases (incl. human body)
Contamination occurs when…
People swallow or breathe in radioactive materials
Can enter body through open wound or absorbed by skin
Can cause cancer or mutated genes
Level of contamination depends on
Penetrating power
Ionising power
Half life of radio isotope
Medical tracer
A radioisotope the is put into the body, by injecting or eating
Uses of medical tracers
Monitor functioning of internal organs
Check for blockage in a pettiness blood vessel
Irradiation
Where an object is exposed to nuclear radiation
Exposure can originate from various sources such as natural sources and background radiation
Sources we are irradiated from
Sky- 400000 cosmic rays pass through us per hour
Air- 30000 atoms of radioactive gases are breathed in and disintegrate into our lungs per hour
Food- 15 million potassium-40 atoms disintegrate into our bodies per hour
Soil & building materials- +200million gamma rays pass through us per hour
Irradiation uses
sterilise food in hospitals
Therapeutic purposes
Supermarkets to kill bacteria on fresh food
Effects of irradiation
Cell death
Accurate repair
Misrepair causing mutation
Electromagnetic spectrum
Radio waves Microwaves Infrared radiation Visible light Ultraviolet X-rays Gamma rays
Radioisotopes used in medicine must
Mainly emit gamma rays
Have suitable half life
Not toxic to humans
Radiotherapy
Cancer cells can be destroyed by exposing the affected area of the body to extremely large amounts of radiation
Nuclear radiation is used to destroy or control unwanted tissue
X-rays are preferred to gamma rays because
Produced when needed
Rate of production can be controlled
Energy can be changed
Can not change rate or energy of gamma rays
How to protect healthy tissue
Source is slowly rotated around the patient with the tumour at the centre of the circle
Source is used in 3 different directions around the target area
Brachytherapy
Small sealed radioactive source or seed is placed in tumour
Treat cancer in prostate gland, cervix and womb
Sometimes additionally used to external radiotherapy
Cancer treatment side effects
Vomitting
Reddening and pain in the skin like sunburn
Greater risk of infection
Tiredness
Benefits of nuclear radiation
Explore internal organs
Destroying or controlling unwanted tissue
Tracers used
Health of patient
Radiation dose
Measure of harm that the treatment can give you
Measured in millisieverts (mSv)
Max radiation dose in a year is 20mSv
Nuclear fission
When a large and unstable nucleus splits with the release of lots of energy
Unstable nucleus absorbs neutron splits into 2 daughter nuclei emitting kinetic energy and gamma rays and a neutron
This causes a chain reaction
Nuclear power station
Fission
Has fuel rods which contain radioactive material
Control rods are put between fuel rods to absorb neutrons so process isn’t as quick
Nuclear fusion
The joining of small nuclei such as hydrogen and helium to form a heavier nucleus
Energy source for stars like the sun
Creates lots of thermal energy
Hydrogen fuse at extremely high pressures and temp 10mill degrees
No waste products and easy to obtain hydrogen from sea
Fusion bombs
1952
Stated with fission reaction
Creating high temp for fusion reaction
More powerful than atomic bombs
