Radioactivity Flashcards
What size are small molecules
10(-10)m
Why are atoms neutral
Because they have the same number or protons and electrons and they have an equal but opposite charge
What do electrons do in an atom
The orbits the nucleus at different set distances from the nucleus
When do electrons change orbit
When there’s absorption or emission of electromagnetic radiation
How do atoms form positive ions
If an outer electron absorbs radiation with enough energy it can move so far that it leaves the atom and is now a free electron and the atom is said to have ionised and is now a positive ion - there are now more protons than electrons
What are alpha, beta minus, positron, gamma rays and neutron radiation emitted from and how
From an unstable nuclei in a random process
What are alpha, beta minus, positron and gamma rays all
Ionising radiations
What is background radiation
The low level radiation that is around us all the time
What is alpha radiation
When an alpha particle is emitted from the nucleus
What is a beta minus particle
A fast-moving electron released by the nucleus
What is a beta plus particle
A fast moving positron (the antiparticle of the electron)
Mass of a beta minus particle
No mass
Charge beta minus particle
-1
Mass of beta plus particle
0.0005(same as electron)
Charge of beta plus particle
+1
What is an alpha particle equivalent too
A helium nucleus
What is a beta particle
An electron emitted from the nucleus
What is a gamma ray
An electromagnetic radiation
Where does background radiation come from
Radioactivity of naturally occurring unstable isotopes (in air, some foods, building mats), radiation from space aka cosmic rays - mostly from sun, radiation due to human activity e.g. fallout from nuclear explosions or nuclear waste
How can radioactivity be measured
Using a Geiger-müller tube - which clicks each time it detects radiation
Or photographic film - more radiation the films exposed to, the darker it becomes
How ionising are alpha particles and why
Stonefly ionising because of their size
How ionising are beta particles
Moderately ionising
How ionising are gamma rays and why
Weakly ionising because they tend to pass through rather than collide with atoms
Process of beta minus decay
An atom converts one of its neutrons into a protons while releasing an electron
Process of beta plus decay
a proton in the parent nucleus decays into a neutron that remains in the daughter nucleus, and the nucleus emits a neutrino and a positron,
What happens to the mass and atomic number to alpha decay
Mass number decreases by 4
Atomic number decreases by 2
What happens to the mass and atomic number to beta minus decay
Mass number doesn’t change
Atomic number increase by 1
What happens to the mass and atomic number to beta plus decay
Mass number doesn’t change
Atomic number decreases by 1
What happens to the mass and atomic number to neutron emission
Mass number decreases by 1
Atomic number stays the same
What happens to the mass and atomic number of gamma rays
Neither change
What form are nuclear equations written in
Atoms before decay — atom after decay + radiation emitted (alpha, beta minus, beta plus, neutron emission)
What often happens to nuclei that have undergone radioactive decay
The often undergo nuclear rearrangement with a loss of energy as gamma radiation
What is activity
The rate at which a source decays
How does the activity of a radioactive source decrease over a period of time
Each time a radioactive nucleus decays, one more radioactive nucleus disappears, as the unstable nuclei all steadily disappear, the activity as a whole will decrease
What is half-life
The average time taken for the number of radioactive nuclei in an isotope to halve
What is the unit of activity of a radioactive isotope
Becquerel, Bq
What is a random process and how can we calculate it
Radioactive sources contain radioactive isotopes that give out radiation from the nuclei of their atoms -process=random
If there are lots of nuclei u can predict how many will have decayed in a given time using half-life
What are the dangers of ionising radiation
It can enter living cells and ionise atoms and molecules within them-lead to tissue damage
Lower doses tend to cause minor damage without killing the cells, can give rise to mutant cells dividing uncontrollably-cancer
Higher doses can kill cells completely -lead to radiation sickness
Dangers of beta and gamma radiation
Can penetrate the body and get into vital organs
Alpha cannot penetrate skin
How can we prevent harm caused by ionising radiation
Hospitals limit staff and patient exposure to radiation e.g. shielding is used protecting staff and untreated body parts white short half-life used
What are the differences between irradiation effects and contamination effects
Contamination- contaminating atoms can decay and release radiation, radioactive particles could get in your body and the person becomes contaminated
