1) Radioactivity Flashcards
what did J.J. Thompson discover?
- electrons can be removed from an atom
- so an atom must have smaller parts
what is the plum pudding model and who discovered it?
- Rutherford and Marsden
- firing alpha particles at thin gold foil and seeing how many went through
what is the current model of the atom?
- positively charged nucleus
- negatively charged electrons
what is the relative mass of a proton?
1
what is the relative mass of a neutron?
1
what is the relative mass of an electron?
0.0005
what is the relative charge of a proton?
+1
what is the relative charge of a neutron?
0
what is the relative change of an electron?
-1
what is the charge of the nucleus of each element and how if it different to isotopes?
- positive charge in the nucleus of each element
- isotopes differ in mass by having different numbers of neutrons
in an atom the number of protons is equal…
to the number of electrons so atoms are neutral
when are electrons able to change orbit?
when there is absorption or emission of electromagnetic radiation
what happens if an atom looses an outer electon?
become positive ion
how is beta minus, positron, gamma rays and neutron radiation emitted?
emitted from unstable nuclei in a random process
what are better minus, positron and gamma rays?
ionising radiations
what is meant by background radiation?
-low level radiation that surrounds us all the time
where does background radiation come from?
- human activity, nuclear waste
- space
- naturally, air, foods, building materials
how can we monitor radiation and stop irritation?
- medical people wear photographic film badges to monitor exposure
- keep things in lead boxes
what is an alpha particle equivalent to?
helium nucleus
what is a beta particle?
an electron emitted form the nucleus
what is a gamma ray?
electromagnetic radiation
how do alpha particles behave in terms of penetrations and ionising?
- dont penetrate far, quickly absorbed by materials
- strongly ionising because of size
how do beta particles behave in terms of penetrations and ionising?
- moderately ionising
- beta- has a range of a few meters in air and abroad by aluminium
- beta+ have small range
how do gamma particles behave in terms of penetrations and ionising?
- penetrate far into materials with being stopped
- weakly ionising
what happens in the process of b- decay?
a neutron becomes a proton and an electron
what happens in the process of B+ decay?
a proton becomes a neutron and a electron
what happens to nuclei which has often undergone radioactive decay?
they undergo nuclear rearrangement with a loss of energy as gamma radiation
how does the activity of a radioactive source decrease over time?
- as it decays a radioactive nucleus disappears
- activity decreases
- never reaches 0
- half life
what is the unit of activity on a radioactive isotopes?
becquerel Bq
what is the half life?
time taken for half the undecided nuclei to decay or the activity of a source to decay by a half
can it be predicted when a particular nucleus decays?
- not be predicted
- half life enables large number of nuclei to be predicted
HALF LIFE EQUATIONS
HALF LIFE EQUATIONS
what are the dangers of ionising radiation?
- tissue damage
- mutations, cancer
what is the safety done to protect people from radiation?
- medical, limiting doctors and patients by shielding
- limiting doses for patients as it kills too many cells
what is contamination?
- radioactive partiales on objects
- may decay leasing radiation
what are irradiation effects?
-exposure to radiation
