Radioactivity Flashcards
who discovered radioactivity
Henri Becquerel
how did henri becquerel discover radioactivity?
while studying uranium salts
what did the curies (mary + pierre) discover?
2 new radioactive elements: polonium and radium
what is alpha decay
helium nucleus
what is beta decay
fast moving electrons
how is beta decay formed
when a neutron is converted into a proton and an electron, and the electron is ejected from the nucleus
what is gamma decay
high energy electromagnetic radiation
what is alphas penetrating power
low- penetrates up to a sheet of paper/air
what is betas penetrating power
medium: penetrates up to 5mm of aluminium
what is gammas penetrating power
high-can penetrate up to a thick piece of lead
what is the mass of alpha
heavy
what is the size/mass of beta
light
what is the mass of gamma
not applicable as it is not a particle so it has no mass
what is the speed of alpha
slow (slowest of the 3)
what is the speed of beta
fast (faster than alpha
what is the speed of gamma
very fast: fastest of the 3
how does alpha deflect in a magnetic field
attracts to negative plate
how does beta deflect in a magnetic field
attracts to positive plate
how does gamma deflect in a magnetic field
no effect
what are the uses of alpha
smoke detectors- americium 241
what are the uses of beta
carbon-14 dating
iodine-131 measures iodine uptake by thyroid
what are the uses of gamma
cobalt-60 used to sterilise medical equipment
is alpha dangerous
only of inhaled or ingested will it cause cancer as it cannot penetrate skin
is beta dangerous
yes. it can be absorbed by the skin and can cause sunburn but it is most dangerous when ingested or inhaled
is gamma dangerous
yes. can penetrate skin easily and will cause cancer
nuclear reaction
process that alters the composition, structure, or energy of an atomic nucleus
give 3 differences between nuclear and chemical reactions
nuclear:
involves changes to the nucleus
a new element is formed
no chemical bonds are formed or broken
chemical:
involves electrons not the nucleus
no new elements are formed
chemical bonds are broken and formed
radioisotopes
a radioactive isotope ie carbon-14
radiocarbon dating
a technique used to determine the age of an object containing carbon. it is based on the ratio of carbon-14 to carbon-12 in the object
explain how radiocarbon dating works
the ratio of carbon 12 to carbon 14 is constant in living organisms
when the organism dies no more carbon 14 is taken in and the carbon 14 already present in the organism decays. by measuring the ratio of carbon 12 to carbon 14 the age of the item can be calculated
sources of background radiation
radon gas
nuclear weapons testing and accidents like Chernobyl
what equipment is used when investigating radiation
geiger muller tube
rate meter
sheet of paper
5mm sheet of aluminium
alpha beta and gamma sources
blocks of lead
what is a geiger counter?
a geiger muller tube and a rate meter joined
what is a geiger muller tube
a sensing instrument used to detect radiation
what does a rate meter do?
counts the number of radioactive particles that enter the GM tube per second
what is the procedure when investigating radiation
measure background level of radiation
using a tongs and gloves hold alpha particle source close to the geiger muller tube
note increase in radiation detected
hold sheet of paper between alpha and GM tube
number of radiation detected should drop
repeat for beta (replacing sheet of paper with aluminium) and gamma (replacing sheet of paper for a block of lead)
explain why it is impossible to change Pb into Au by a chemical reaction
chemical reactions involve electrons only and do not involve changes to the nucleus
changing Pb into Au requires a nuclear reaction to alter the number of protons in the nucleus
write the general formula for an alpha decay reaction
a 4 (a - 4)
X——> He + (X-2)
z 2 (z - 2)
write the general formula for a beta decay reaction
a 0 (a )
X——> e- + (X+1)
z -1 (z + 1)
half life
time taken for half of the nuclei in a given radioactive sample to decay
how do you calculate half life
1.divide how many years its asking for divided by the half life
2. divide the amount in the sample by 2 to the power of your answer in 1.
