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Physics A-level preparation:Particles: - Coggle Diagram
Physics A-level preparation:Particles:
Isotopes:
Different form of the same element with same no. protons, different no. neutrons
Unstable isotopes need to decay into other elements, releasing radiation, in order to become stable (radioactive decay)
Current nuclear model:
Positively charged
nucleus containing
neutrons
and
protons
Nucleus surrounded by
negatively charged electrons
orbiting it in fixed energy levels
The atom is of neutral charge as there is an equal number of protons and electrons, cancelling out the charge
Radius of atom= 1x10^-10 m
Further
the electron is from nucleus,
closer
the energy levels so difference in energy gets smaller
The release and absorption of electrons:
The further away the electron from nucleus, more energy is has, though it doesn't release or absorb as much energy as energy levels are closer
When electrons in inner shells
gain energy (by absorbing EM radiation)
, they
move to a higher energy level.
The electrons have been
excited
Can
only absorb the exact amount
that allows them to move between energy levels.
Electrons fall to a
lower energy level
if they
lose energy (by releasing EM radiation
The
higher amount of energy
that is being gained or lost, the
higher frequency of EM radiation.
Ionisation
Absorbing too much radiation can cause an electron to leave the atom (atom is
ionised
)
Produces a positive ion
More protons than electrons
Types of decay:
Alpha
Equivalent to a helium nucleus
(2 neutrons and 2 protons)
Relative charge: 2+
Relative mass: 4
Highly ionising
Don't penetrate far into materials
Few cm in air, absorbed by a piece of paper
Beta
Beta-minus particle (B-)
Relative charge: -1
Fast moving electron released from the nucleus
Penetrates through a few metres air, absorbed by a sheet of aluminium (approx 5mm thick)
Mass: 0
Beta-plus particle (B+)
Fast moving positron released from the nucleus
Positron:
Antiparticle of electron
Same mass, different relative charge
Relative charge: +1
Smaller range than beta minus as annihilation is caused when they hit an electron. Gamma rays are produced
Moderately ionising
Moderately penetrating
Gamma
Short wavelength EM radiation
Relative charge: 0
Mass:0
Highly penetrating
Absorbed by thick sheets of lead, several metres concrete
Weakly ionising
Used to get rid of energy to stabilise nucleus after other radiation as taken place
Activity and half life:
Activity:
Measured in becquerels (Bq)
Rate of decay
Radiation measured using
Geiger Muller counter
(clicks when it detects radiation)
Radiation detected by
photographic film
which becomes darker the more exposed it becomes.
Half life:
Time taken for activity of a source to decay by half
Time for half the undecayed nuclei to decay