Physics- Atomic structure Flashcards
What is an isotope
An isotope is an element that has the same number of protons, but different number of neutrons.
Alpha particle characteristics
- Are helium nuclei
- Has 2 neutrons and 2 protons
- Don’t penetrate far into materials + are stopped quickly
- can only travel few cm in air + are absorbed by a piece of paper
- Strongly ionising
Beta particle characteristics
- A fast moving electron released by the nucleus
- 0 mass and charge of -1
- Penetrate moderately far into materials before colliding
- Range in air of few meter, absorbed by sheet of aluminium
- Moderately ionising
Gamma ray characteristics
- Waves of electromagnetic radiation released by the nucleus
- Penetrate far into materials without being stopped
- Travel long distance through air and can be absorbed by thick lead or meters of concrete
- Weakly ionising, they pass through rather than collide with atoms
What is a half life?
The time taken for the number of radioactive nuclei in an isotope to halve
What are nuclear equations + how are they written
- They are a way of showing radioactive decay by using element symbols
- Written in the form: atom before decay—> atom after decay + radiation emitted
- Total mass and atomic numbers must be EQUAL on bother sides
What does alpha decay do to the charge + mass of the nucleus
- Alpha decay DECREASES the charge + mass
- Atomic number reduces by 2
- Mass number reduces by 4
What does beta decay do to the charge and mass of the nucleus?
- Beta decay INCREASES the charge but the mass STAYS THE SAME
- a neutron in the nucleus turns into a proton + releases a fast moving electron (the beta particle)
- Number of protons in the nucleus has increased by 1 - increasing the + charge (atomic number)
- lost electron and gained proton- mass doesn’t change.
What do gamma rays do to the charge + mass of the nucleus?
- Gamma rays DON’T CHANGE the charge or mass
- way of getting rid of excess energy
- no change to atomic mass or atomic number
What is background radiation?
- Background radiation is the low-level radiation that’s around us all the time
- You should always measure and subtract the background radiation from your results
What are the sources of background radiation?
- Radiation from space- cosmic rays- from the sun. Earths atmosphere protects us.
- Radiation of naturally occurring unstable isotopes
- Radiation due to human activity
What is irradiation?
- Something is irradiated when it’s been exposed to a radioactive source
- Irradiating something doesnt make it radioactive
What is contamination?
- When unwanted radioactive atoms get onto or into an object
- Contaminating atoms might then decay, releasing radiation which could cause harm
- Wear protective gear and use tongs when handling sources
What is the seriousness of each source outside the body?
- Beta and gamma most dangerous - both can penetrate the body and get to the delicate organs
- Alpha is less dangerous- can’t penetrate the skin- easily blocked by small gap of air
What is the seriousness of each source inside the body?
- Alpha is most dangerous- highly ionising- do all damage in localised area
- Beta is less dangerous- moderately ionising- radiation absorbed over wider area
- Gamma lest dangerous- leat ionising- mostly pass straight out
What are nuclear radiations used for in medicine?
- exploration of internal organs
- control or destruction of unwanted tissue (eg radiotherapy)
What type of radioactive source is usually used in medical tracers?
- Gamma
- The radiation passes out of the body without causing too much ionisation
- Should have short half-life so radioactivity inside patient disappears quickly
What is a perceived risks
how risky a person thinks something is
(not the same as the actual risk of a procedure)
What can a tracer be used for and what is the risk
- used to detect life-threatening conditions (positive)
- risk of cancer us very small (negative)
- In this case the positive outweighs the small risk
What is nuclear fission
Type of nuclear radiation used to release energy from large and unstable atoms by splitting them into smaller atoms.
What does nuclear fission release?
Two new lighter elements + two or three neutrons
What is nuclear fusion
- the opposite of nuclear fission
- when two light nuclei collide at high speed and join (fuse) to make larger, heavier nucleus
- Releases a lot of energy
- Found in fusion reactors which are hard and expensive to build
