radioactivity Flashcards
what is the mass number also known as?
the nucleon number
what is the mass number?
n. of protons & neutrons
what is the atomic number also known as?
the proton number
what is the atomic number?
n. of protons
what are isotopes?
atoms with the same number of protons but different number of neutrons
why is a radioisotope unstable?
it has too many neutrons- decays and emits radiation randomly
radioisotopes randomly emit alpha or beta particles or gamma radiation to form what?
a new atom with a different number of protons
where is radiation emitted from?
the nucleus of an unstable atom
radiation happens…
randomly
radiation from a nucleus can take what 3 forms?
- alpha
- beta
- gamma
what is an alpha particle?
- a helium nucleus
- 2 protons, 2 neutrons
what charge does an alpha particle have?
+2 charge
are alpha particles fast or slow?
quite slow
are alpha particles big or small?
massive (relatively)
what does radium become when it decays?
radon
what is a beta particle?
- a very fast electron emitted from the nucleus
what is the charge on a beta particle?
-1 charge
are beta particles fast or slow?
fast
do beta particles have a big or small mass?
very small mass
what is a gamma wave?
- an electromagnetic wave- very short wavelength, very high frequency
do gamma waves have a charge?
no charge
are gamma waves slow or fast?
extremely fast- speed of light (3 x10 to the power of 8)
what is the mass of an alpha particle?
4u- heavy (massive)
what is the mass of a beta particle?
- 1/1850
- very small
what is the mass of a gamma wave?
0
what is the penetrating power like for alpha particles?
- low
why is penetrating power low for alpha particles?
- cannot get through materials easily
- stopped by 5cm of air & by thin aluminium
what is the penetrating power like for beta particles?
mid power
why do beta particles have medium penetrating power?
stopped by mm of aluminium
what is the penetrating power like for gamma waves?
high
why is the penetrating power high for gamma waves?
- stopped by thick lead or concrete
- can travel long distances in air
what is ionisation?
the process of adding or removing electrons from atoms
do alpha and beta have lots of kinetic energy?
yes- they are moving fast
what is half life?
the time taken for half the radioactive nuclei to decay
why do we measure half life?
- the decaying process is random
- we can’t measure the whole life of a radioactive material
- so we have to measure half life
how is the beta electron formed?
when a neutron in the nucleus splits into a proton and an electron
the beta electron (negative) is always…
0
-1
how is a positive ion left behind?
the radiation provides energy to allow outer shell electron to escape the pull of the nucleus- leaving a positive ion behind