RADIOACTIVITY AND PARTICLES Flashcards
what is the nucleus?
- an atom made up of protons and neutrons
- the number of protons determines what element the nucleus is
what are isotopes?
- contain the same number of protons, but a different number of neutrons
- same atomic number, different mass number
what is the number of protons in the nucleus known as?
- atomic number or proton number
what is the number of protons plus neutrons known as?
- mass or nucleon number
what is the mass of the nucleus?
relative atomic mass
what are unstable nuclei?
- emit particles, or energy, in order to become stable again
- these unstable nuclei are called radioactive nuclei
what is the unit for radioactive activity?
becquerel (Bq)
one becquerel is one decay per second
three types of radioactive decay:
- alpha
- beta
- gamma
what are alpha particles?
made of two protons and two neutrons bound together
what speed are alpha particles emitted at?
10% the speed of light
what charge do alpha particles have?
+2
are alpha particles highly or lowly ionising?
highly ionising
what are alpha particles stopped by?
a few centimetres of air or a sheet of paper
what are beta particles?
an electron emitted when a neutron in the nucleus is turned into a proton
what speed are beta particles emitted at?
50% the speed of light
what charge do beta particles have?
-1
are beta particles weakly or highly ionising?
weakly ionising
what are beta particles stopped by?
a few millimetres of aluminium
what is a gamma ray?
high energy electromagnetic wave
what speed to gamma rays travel at?
the speed of light
are gamma rays highly or weakly ionising?
weakly ionising
what are gamma rays stopped by?
a few centimetres of lead
background sources of radioactivity:
- radon gas
- medical exposure
- rock
- cosmic rays
what happens to the atomic and mass number when you emit an Alpha particle?
atomic number lowers by two
mass number lowers by four