6.4 Nucleur and particle physics Flashcards
Define proton number, nucleon number and isotopes?
-Proton number: the number of protons inside the nucleus of a particular atom, also known as mass number
-Nucleon number: the number of nucleons (protons and neutrons) inside the nucleus of a particular atom, also known as mass number
-Isotopes: atoms of the same element which contain the same number of protons but different number of neutrons
Describe Rutherfords alpha particle scattering experiment?
- Rutherford fired alpha particles at a thin gold foil to see how they were deflected, he had a detector which flashed when an alpha particle hit it
- Most alpha particles travelled straight through and a small number where deflected by an angle less than 90° however a very small number of alpha particles bounced back through an angle greater than 90°
What was the conclusions from the alpha particle scattering experiment?
-The majority of the mass of an atom was contained within a small volume nucleus
-Nucleus has a positive charge
-The nucleur diameter is considerably smaller than the diameter of the atom, so the atom is mostly empty space
What is the charge/mass of a proton, neutron and electron?
Proton: 1e/1u
Neutron: 0e/1u
Electron:-1e/1÷1840u
What is the strong nuclear force and why is it needed?
-The force that acts between the nucleons and holds together the nucleus against the electrostatic repulsion of the protons
What are the properties of the strong nuclear force?
-The strong nuclear force acts within the nucleus but decreases rapidly with distance
-The nuclear force is not just an attractive force because otherwise nucleons would collapse in on themselves
-It provides a repulsive force for seperation up to 0.5fm anf provides an attractive force for distances between 0.5-3fm
What is the relationship between nucleon number and nuclear radius?
-The nucleur radius is directly proportional to the cube root of the nucleon number(mass number)
What is the equation for nuclear radius?
R=Nuclear radius
r₀= 1.4fm(*10^-15)
A= nucleon number
What is the equation for nuclear density?
p=density
r₀=1.4fm
mₙ = mass of nucleons
What are the definitions of fundamental particles, hadrons, leptons and quarks?
-Fundamental particles: are particles that cannot be brocken down into smaller components
-Hadrons: particles consisting of quarks to give a net zero or whole number of charge, neutrons and protons are hadrons
-Leptons: fundamental particles, electrons and neutrinos are leptons
-Quarks: components of hadrons, they have fractional electric charge, there are different types e.g up, down and strange
What is a neutrino, the weak nuclear force and an antiparticle?
-Neutrino: a fundamental particle with almost no mass and zero charge
-Weak nuclear force: force felt by both quarks and leptons and can change quarks from one type to another or leptons, it is responsible for beta decay
-Antiparticle: is a particle of anitmatter it has the same rest mass but opposite charge to the particle
What is the charge of up, down and strange quarks?
-Up: +2/3e
-Down: -1/3e
-Strange: -1/3e
e-elementary charge
What is the charge of up,down and strange antiquarks?
-Up: -2/3e
-Down: +1/3e
-Strange: +1/3e
What is the baryon number of a quark and an antiquark?
-Quark: 1/3
-Antiquark: -1/3
What is an alpha particle, beta particle and a gamma ray?
-Alpha particle(α): a particle consisting of two neutrons and two protons, it is identical to a helium nucleus
-Beta particle(β): high speed electron emitted during beta decay, when a neutron changes into a proton
-Gamma ray(γ): a form of electromagnetic radiation with wavelengths between 10^-16
and 10^-9m
Why is radioactive decay spontaneous and random?
-Radioactive decay is spontaneous because its isn’t affected by any external factors for e.g. temperature
-Radioactive decay is random becuase you can’t tell which particles will decay or how many
Describe the penetration of alpha and beta particles and gamma rays?
-Alpha particles are highly penetrative so would be stopped by a few cms of air
-Beta particles are less so would travel a few ms in air and be stopped by thin aluminium
-Gamma rays are the least penetrative so would pass through paper and aluminium but be stopped by thick lead
What is the charge of an alpha particle, beta particle and gamma rays?
-Alpha particles: +2e
-Beta particles: -e
-Gamma particles: zero
How can you carry out an investigation to determine the absorption of alpha particles, beta particles and gamma rays?
1.Set up apparatus as shown and take safety precautions for radioactive materials e.g using a tool rather than fingers to touch source
2.Geiger-muller tube is used to detect the radiation passing through the different materials
3. Measure a backround radiation and subtract from the results, measure the amount of different types of radiation that passes through the different materials
What is A and Z?
A-Nucleon number
Z-proton number
Draw the nuclear equation for the alpha decay of uranium(238) into Thorium (234)?
What are the two types of beta decay?
-Beta decay or beta-minus decay and beta plus decay
What happens during beta decay/beta minus decay of carbon into nitrogen?
-A neutron in the nucleus turns into a proton, an electron and an electron antineutrino are ejected from the nucleus (this is the beta minus particle)
What happens during the beta plus decay of florine into oxygen?
-A proton in the nucleus turns into a neutron, a positron and a neutrino are emitted
What types of nuclei does beta decay and beta plus decay happen to?
-Beta decay: nuclei that are unstable with low mass and too many neutrons
-Beta plus decay: nuclei with too many protons
Why do gamma rays usually acompany other radiation types?
-Gamma rays help remove energy leading to more energetically stable nucleus after decay
Draw a graph showing the zone of stability of nuclei?
