Topic 4 Atomic Structure Flashcards
What can electrons do if they gain energy by absorbing EM radiation?
Move to higher energy level- further from nucleus
What can electrons do if they emit/release EM radiation?
Move to lower energy level- closer to nucleus
What does EM radiation stand for?
Electromagnetic
What is radioactive decay?
Unstable nuclei decay to become more stable, emitting radiation in process
What is ionising radiation?
Knocks electrons off atoms, creating positive ions
What are the 4 things a nucleus can emit in radioactive decay?
Alpha particle
Beta particle
Gamma ray
Neutron
What is alpha radiation?
alpha particle emitted from nucleus
What is an alpha particle?
2 neutrons and 2 protons (same as helium nucleus)
What is the ionising power of alpha particles?
Strongly ionising
What is the penetrating power of alpha particles?
Absorbed by skin/paper
How far can alpha particles travel in air?
< 5cm
What is the symbol for an alpha particle?
a
What is a beta particle?
Fast moving electron released by nucleus
What is the ionising power of a beta particle?
Moderately ionising
What happens every time a beta particle is emitted from a nucleus?
Neutron turns into proton
What is the penetrating power of a beta particle?
Absorbed by 3mm aluminium foil
How far can beta particles travel in air?
Metre/a few metres
What is a gamma ray?
Wave of electromagnetic radiation emitted from nucleus
What is the ionising power of a gamma ray?
weakly ionising (pass through rather the collide with atoms)
What is the penetrating power of a gamma ray?
Absorbed by lead/concrete
How far can a gamma ray travel in air?
> kilometre
What are nuclear equations used to represent?
Radioactive decay
What form are nuclear equations written in?
Atom before decay > atom after decay + radiation emitted
What is the symbol for a gamma ray?
y
What is the symbol for a beta particle?
B
What 2 things happen when an atom emits an alpha particle?
Atomic number reduces by 2
Mass number reduces by 4
What does alpha decay cause the mass and the charge of a nucleus to do?
Decrease
How is an alpha particle written in nuclear equations?
As a helium nucleus
What happens to the number of protons in the nucleus when beta decay occurs?
Increases by 1
What happens to the charge of the nucleus when beta decay occurs?
Increases-
Why does the mass of the nucleus not change when beta decay occurs?
Neutron lost but proton gained- same mass
How is a beta particle written in nuclear equations?
As an electron
What happens to the atomic number when beta decay occurs?
Increases by 1 (proton gained)
What happens to the charge and mass of the nucleus when a gamma ray is emitted?
No change
What type of process is radioactive decay?
Random
What is count-rate?
Number of decays recorded each second by a detector
What is the name of the detector that records count-rate?
Geiger-Muller tube
What is activity?
Rate at which source of unstable nuclei decays
What is activity measured in?
Becquerels Bq
What is background radiation?
Low-level radiation around us all the time
What are 2 things background radiation comes from?
Natural resources
Man-made sources
What are 2 examples of natural resources that are sources of background radiation?
Cosmic rays from space
Rocks
What are 2 examples of manmade sources of background radiation?
Fallout from nuclear weapons testing
Nuclear accidents
What does radiation dose tell you?
Risk of harm to body tissues due to radiation exposure
What is radiation dose measured in?
Sieverts (Sv)
What 2 things does the level of background radiation and your radiation dose depend on?
Occupation and location
What is irradiation?
Exposing an object to nuclear radiation
What does irradiating something not do?
Make it radioactive
What are 2 ways of reducing the effects of irradiation?
Keeping sources in lead-lined boxes
Standing behind barriers
What is radioactive contamination?
Unwanted material containing radioactive atoms on other materials
Why is contamination harmful/hazardous?
Contaminating atoms decay, releasing radiation
What are 3 ways of protecting against contamination?
Gloves
Using tongs
Wear protective suits
How does wearing a protective suit prevent contamination?
Prevents breathing in particles
How does using gloves and tongs prevent contamination?
Avoids particles getting stuck to skin/under nails
What does the level of hazard/harm of contamination or irradiation depend on?
Type of radiation emitted
Which 2 radiation sources are most dangerous outside the body (irradiation)?
Beta and gamma
Why are beta and gamma the most dangerous outside the body?
Penetrate body and get to delicate organs
Why is alpha less dangerous outside of the body?
Can’t penetrate skin and easily blocked
When is irradiation dangerous from all sources?
High levels
Which type of radiation is most dangerous inside the body (contamination)?
Alpha
Why is alpha the most dangerous inside the body?
Most ionising, causes damage in very localised area
Why is it so important that research into the effects of radiation on humans is published and peer-reviewed?
Become quickly accepted, improve our use of radioactive sources
What is the risk of radiation entering living cells?
Ionise atoms/molecules within cells- tissue damage
What is risk of lower doses of radiation?
Cause minor damage without killing cells, lead to cancer (mutant cells divide uncontrollably)
What is the risk of higher doses of radiation?
Kill cells completely, causes radiation sickness
What are 3 symptoms of radiation sickness?
Vomiting
Tiredness
Hair loss
What 2 things are nuclear radiations used in medicine for?
Exploration of internal organs
Destroying unwanted tissue (treating cancer)
How can internal organs be explored using a tracer?
Radioactive isotopes injected/swallowed, their progress around body followed using external detector
What is treating cancers using ionising radiation known as?
Radiotherapy
Why can high doses of ionising radiation be used to treat cancers?
Kill all living cells
How are gamma rays used to treat cancer?
Directed into body and kill cancer cells
What are the 2 ways of treating cancer using radiation?
- external gamma rays
- internal radiation-emitting implants
How can radiation emitting implants be used to treat cancer?
Put next to/inside tumours
What is the advantage of treating cancer using radiation-emitting implants?
Targets tumour very precisely- less damage to healthy tissue
What is the disadvantage of using external gamma rays to treat cancer?
Fair amount of damage to healthy tissue- patient feels ill
What is the perceived risk?
How risky a person thinks something is
What type of radioactive isotopes are usually used in medical tracers?
Gamma sources
What are the 2 things radioactive isotopes entering the body should have?
Pass out body without causing much ionisation
Short half life so radioactivity quickly disappears
What is an example of a radioactive isotope used to explore internal organs?
Iodine-23, show whether thyroid gland taking in iodine
What are medical tracers used for?
Exploration of internal organs
What is nuclear fission?
Splitting of a large and unstable nucleus
What are 2 examples of large unstable atoms?
Uranium
Plutonium
What is nuclear fission used for?
Release energy from large unstable atoms by splitting into smaller atoms
What is rare (nuclear fission)?
spontaneous (unforced) fission
What usually has to happen for fission to occur?
Unstable nucleus absorb neutron
What does a nucleus undergoing fission split into?
2 smaller nuclei, roughly same size
What do all fission products have?
Kinetic energy
What 3 things are emitted when a nucleus splits?
2 or 3 neutrons
Gamma rays
Energy
How can the neutrons emitted in fission go on to start a chain reaction?
If neutrons moving slow enough, absorbed by another nucleus, more fission occurs
What is the amount of energy produced by fission in a nuclear reactor controlled by?
Changing how quickly chain reaction can occur, using control rods
How are the control rods used to control the energy released in fission?
Lowered and raised in nuclear reactor
How do nuclear weapons work?
Uncontrolled chain reactions quickly lead to lots of energy released as explosion
What is nuclear fusion?
2 light nuclei collide at high speed and join to create larger, heavier nucleus
What is an example of nuclear fusion?
Hydrogen nuclei fuse to produce helium nucleus
What happens to some of the mass of the lighter nuclei in nuclear fusion?
Converted to energy and released
Why have scientists not yet found a way of using fusion to generate energy for us to use?
Temperatures and pressures needed so high that fusion reactors very hard and expensive to build
What do radioactive isotopes have a very wide range of?
Half lives
What happens each time a radioactive nucleus decays to become a stable nucleus?
Activity as whole decreases
What is the half life?
Time taken for number of radioactive nuclei in isotope to half
Why do we use half life?
Activity never reaches zero, measure how quickly activity drops of
What is the other definition of half life?
Time taken for activity/count rate to halve
What does a short half life mean?
Nuclei very unstable and rapidly decay
Why are sources with a short half life dangerous?
High amount of radiation emit at start, quickly become safe
What does a long half life mean?
source releases small amounts of radiation for long time
Why are sources with a long half life dangerous?
Nearby areas exposed to radiations for (millions of) years
