Particles Flashcards
Name parts of the atomic model
Protons
Neutrons
Electrons
Describe the atomic model
A dense nucleus containing protons and/or neutrons that has electrons orbiting around it in energy levels
Mass of a proton?
1.67 x 10^-27 (Kg)
Charge of a proton?
+1.60 x 10^-19 (C)
Charge of a neutron?
0
Mass of a neutron?
1.67 x 10^-27 (Kg)
Mass of an electron?
9.11 x 10 ^-31 (Kg)
Charge of an electron?
-1.60 x 10^-19 (C)
Relative charge and mass of an Electron?
Relative charge: -1
Relative mass: 0.0005
Relative charge and mass of an Proton
Relative charge: +1
Relative mass: 1
Relative charge and mass of an Neutron?
Relative charge: 0
Relative mass: 1
What is the atomic number?
Number of protons in an atoms nucleus
Significance of protons and electrons?
Protons define elements
Electrons define how they will react
What is the nucleon number?
The amount of protons and neutrons in an atom
Is also often the RELATIVE mass of an atom
Define an isotope?
An isotope is an atom with the same amount of protons but a different amount of neutrons
What effect does having different amounts of neutrons in an atom have?
No effect on the chemical properties of the atom,
however it will effect the stability of the atom and it may be radioactive and decay over time
Uses of an isotope?
Can be used to see how old an organism is
All living things have the same %age of carbon-14, as it decays when it dies carbon-14 decays into other elements
The amount of carbon-14 left can be used to deduct how old something has been dead for
What is specific charge?
The ratio of the particle’s charge per unit mass
Given in CKg^-1
Equation for specific charge?
Specific charge = charge
—————
mass
If the gravitational force is weaker than the electrostatic force in an atom, what holds it together?
The strong nuclear force
What is the strong nuclear force?
Holds atoms together
How does the strong nuclear force work?
If Nucleons are less than 0.5 femtometres apart they will be repulsive
Strong nuclear force has to be larger than electrostatic (electrostatic only occurs between protons so is repulsive) force
Between 0.5 and 3 femtometres the force is its most attractive
After 3 femtometres the force falls rapidly towards 0
Basic Features of the strong nuclear force?
Only works when nucleons are a few femtometres away
Strong Nuclear force must be stronger than electrostatic force for it to be stable and hold atom together
Strength of the strong nuclear force falls off quickly
Size of the force is equal between all nucleons
It can be repulsive when lower than 0.5 femtometres apart
When does alpha decay occur?
Only happens in very large unstable nuclei
What happens when an alpha particle is emmitted?
From the original particle the daughter particles nucleus’ proton number decreases by 2 and the nucleon number decreases by 4 - and an alpha particle emitted
Essentially from the original particle releases a daughter particle and helium
What is Beta (minus)decay?
When does it happen?
It is when an electron and an anti-neutrino are emitted from the nucleus and a neutron turns into a proton
Occurs when there are too many more neutrons than protons
What happens when beta minus decay occurs?
An electron and an antineutrino are emitted from the nucleus of the atom, then a neutron turns into a proton
So from the original particle the proton number increases by 1 and the nucleon number stays the same
What happens when beta minus decay occurs?
An electron and an antineutrino are emitted from the nucleus of the atom, then a neutron turns into a proton
So from the orginal particle the proton number increases by 1 and the nucleon number stays the same
Why is there an antineutrino in beta minus decay?
Observations showed that there was less energy after the decay than before, and they originally thought it was just an electron emitted.
Due to conservation of energy another neutral charged and almost massless particle must also be emitted
25 years later Wolfgang Pauli’s particle was discovered and named the neutrino
What is photon?
It is a packet of electromagnetic radiation
What equation links the speed, wavelength and frequency of an electromagnetic wave? (in a vacuum)
c=f x lambda wave speed (m/s) = frequency(Hz) x wavelength (m)
As a photon is a packet of electromagnetic radiation what is the equation that links photon energy and EM radiation together?
E= h x f = (h x c)/lambda
Photon energy(J) = planck’s constant x frequency (Hz) = (planck’s constant x wave speed(m/s))/lambda(m)
What is planck’s constant?
6.63x10^-34(J)
When a particle is made _______________?
An antiparticle is made with the same mass and rest energy but opposite charge
What is 1 Mev equal to in eV?
1 Mev = 1 x 10^6 eV
What is Einstien’s theory of relativity suggest?
Suggests that energy can turn into mass and vice versa
What does ‘rest energy’ mean
It’s the energy equivalent of the particle’s mass measured in MeV
What is the equation that is used in Einstein’s theory of relativity?
E=mc^2
Energy(J) = mass(Kg) x wave speed(m/s) ^2
Examples of Theory of relativity?
If you fire two protons at each other just at the point of impact there will be a lot of energy, this could make a new particle and an anti-particle as a result of it being made
What will happen if you fire 2 protons at each other with enough energy?
Pair production
The result will be:
2 protons that were fired at each other
1 new proton that was made as a result of the energy at impact
1 anti proton as a result of the proton being made
What happens when particles are produced in pair production in terms of photons?
The initial energy that converts into matter and anti matter is in the form of 1 photon
What is meant by the minimum energy in pair production?
The photon needs to have enough energy to pair produce
The minimum energy required is the total rest energy of the particles produced
Rest energy = E<0>
Equation for minimum energy in pair production?
E = h x f = 2E<0> (as 2 particles produced)
Min energy required = planck’s constant (J)x frequency(Hz) = OR 2 lots of the rest energy of the particle produced
What is annihilation ?
When an antiparticle and particle meet
What happens in annihilation?
All the mass of the two particles get converted back into energy in the form of 2 photons
What is pair production?
When a photon is converted into matter and anti-matter
Equation for annihilation?
E = h x f = E<0> (as 1 photon produced)
Min energy required = planck’s constant (J)x frequency(Hz) = OR 1 photon with the rest energy of the particles
What is an exchange particle?/Boson
They are virtual particles that allow other particles to interact
As there must be a something that lets one particle know that another is there, as there cannot be instantaneous action at a distance
What happens when particles repel at a subatomic level?
One particle exchanges an exchange particle(or photon) directly towards the other particle
When the exchange particle is sent, the particle is sent in the opposite direction of the exchange particle movement so momentum is conserved
When the exchange particle is received the particle is moved in the opposite direction to which the exchange particle was received
Hence the particles are repelled from each other
What happens when particles attract at a subatomic level?
One particle exchanges an exchange particle(or photon) in the complete opposite direction to the other particle
When the exchange particle sent to the particle, it moves in the opposite direction of the exchange particle movement so momentum is conserved
When the exchange particle is received the particle is moved in the opposite direction to which the exchange particle was received
So the particles move towards each other
Hence the particles are attracted to each other
What are the 4 fundamental forces in particle physics?
Gravity
Weak
Strong
Electromagnetic
Features of the Weak force? and exchange particle?
It affects all particles
Short Range
W+ or W- exchange particles
Features of the Strong force? and exchange particles?
Only effects Hadrons
Pion +, Pion- and Pion 0 are the exchange particles
Features of the electromagnetic force? and exchange particles
Only effects charged particles
Long Range
Photon is the exchange particle
Whats an eV in Joules?
1.6 x 10^-19 J
The larger/ more mass of the Exchange particle the ___________
Smaller the range
