Radioactive Substances Flashcards
What makes a substance radioactive?
radioactive substances emit radiation from its nuclei of their atoms all the time
What are the natural causes of background radiation?
cosmic rays from space
some rocks give off radioactive radon gas
living things emit radiation as plants absorb radioactive materials, as a result they pass up the food chain
What are the artificial causes of background radiation?
medical x-rays
nuclear missiles used to be dropped for testing, this releases radiation
nuclear power stations have released radiation into the atmosphere
What is a alpha and beta particle?
the same as a helium nucleus, contains two neutrons and two protons
a beta particle as an electron from the nucleus
What happens in alpha decay?
two protons and two neutrons are lost when an alpha particle is emitted
atomic mass decreases by 4
atomic number decreases by 2
What happens in beta decay?
a neutron changes into a proton plus an electron
the proton stays in the nucleus
the electron leaves the atom with high energy as a beta particle
atomic mass number stays the same
atomic number increases by 1
What are the properties of alpha radiation?
least penetrating, can be absorbed by a single sheet of paper
most dangerous because it is easily absorbed when it is inside the body
when it is outside the body it is not dangerous because it is unlikely to reach cells in the body
What are the properties of beta radiation?
can penetrate air and paper, but can be absorbed by a thin sheet of aluminium
not as dangerous because it is less easily absorbed when it is inside the body
when it is outside the body it is dangerous because it can penetrate skin and damage the cells
What are the properties of gamma radiation?
most penetrating, even small levels can penetrate metal
can only be stopped by many centimetres of lead or many metres of concrete
not easily absorbed by cells and usually passes straight through cells when it is inside the body
when it is outside the body it is dangerous because it can penetrate skin and damage the cells
How is radiation deflected by electric and magnetic fields?
alpha particles are positively charged,beta particles are negatively charged and gamma is neutral
this means that gamma is not deflected
alpha particles are attracted to the cathode
beta particles are attracted to the anode
alpha particles are deflected less and in the opposite direction beta because of their mass and charge
What are the impacts of radiation on living cells?
when radiation collides with molecules in living cells it can damage them
if DNA in the nucleus is damaged, the cell may become damaged
the cell then divides rapidly and causes serious health problems
high doses can kill cells completely
it can be used to kill cancer cells and microbes
What is half life?
the average time it takes for the number of nuclei of the isotope in a sample to halve,
or the time it takes for the count rate from a sample containing the isotope to fall half its initial level
