Particles and Nuclides Flashcards
What is the Nucleon Number
The number of protons plus the number of neutrons in the nucleus
What is the Atomic/ Proton Number
The number of protons in the nucleus
What is Specific Charge
The charge per unit mass of a particle
What is the Specific Charge Equation
Specific Charge = Q / m
Specific Charge ( C Kg^-1) = Charge (C) / mass (Kg)
What is an Isotope
A nucleus of the same element with the same number of protons but a different number of neutrons
What is the Strong Nuclear Forces Role
To keep the nucleus stable against the electrostatic force
Describe the Forces within the Nucleus
- From 0 - 0.5 fm (femtometers) the strong nuclear force is strongly repulsive and repels the nucleons to stop them from colliding
- There is also strong electrostatic repulsion between charged particles
- At 1.5fm the strong force becomes strongly attractive and holds the nucleons together by equally balancing the repulsive electrostatic force
- This keeps the nucleons stable
- Beyond 3fm the strong force drops to zero and although the electrostatic force has decreased the strong force does not hold the nucleons in the nucleus so the nucleons separate
Describe the Strong Nuclear Force Graph
Describe the Electrostatic Force and Strong Nuclear Force Range
- Electrostatic Force - electrostatic force acts between two charged particles has an infinite range, always repulsive
- Strong Nuclear Force - range of 0-3fm ( the diameter of a small nucleus), attractive/repulsive
What does the strong nuclear force act on
2 protons, 2 neutrons or a proton and a neutron (anything made of quarks)
Why does the strong force need to act between neutrons
Otherwise it would be extremely easy to remove neutrons from the nucleus
Why do nuclei decay
To become stable
What is Alpha decay
The emission of two protons and two neutrons ( same as a helium nucleus)
What happens during Beta minus decay
A neutron turns into a proton and an electron and an anti electron neutrino ( ̅ νe ) are emitted from the nucleus
What happens during Beta plus decay
A proton turns into a neutron and a positron and a electron neutrino (ve) are emitted from the nucleus
What happens during Gamma Decay
When the nucleons lose energy by giving off electromagnetic radiation
Why was the existence of the neutrino hypothesised
To account for the conservation of energy in beta decay
What are the ways of detecting nuclear radiation
- Cloud Chamber
- Spark Counter
- Geiger-Muller Tube
Explain how a Cloud Chamber works
- Creates an artificial cloud of water or alcohol vapour
- As a charged particle flies through it, a visible trace appears
- The bigger the mass, the bigger the trace
- Alpha go towards the negative, Beta go towards the positive and gamma pass straight through
Explain how the Spark Counter works
- A high voltage is set between 2 grids
- As a charged particles flies through it, they produce a spark and sound that can be used to count them
- Only detects highly ionising alpha particles, beta and gamma do not ionise enough in air to be picked up
Explain how a Geiger-Muller Tube works
- A voltage is set up between a cathode and the anode
- As a charged particle flies through it, it’s attracted to one of the two creating a current and a counter reads the current to count particles
- Advance over the other methods as it detects alpha and beta very well
What are the Energy of Photon Equations
- E = hc / λ
- Energy of a Photon (J) = Planck’s Constant (J s) x Speed (m s -1) / Wavelength (m)
- E = hf
- Energy (J) = Planck’s Constant (J s) x Frequency (Hz)
What is an Electronvolt (eV)
1 electronvolt is the energy required to accelerate the charge of 1 electron through 1 volt
What are Antiparticles
Antiparticles have the same mass/ rest-mass energy but opposite charge and other quantum numbers compared to their normal matter counterparts
What is Rest-Mass Energy
The amount of energy released by converting all of the mass into energy
What is Rest Energy
The minimum amount of energy needed to create a particle
What is Annihilation
- When a particle and its corresponding antiparticle collide, as a result their masses are converted into energy
- This energy is released in the form of 2 photons moving in opposite directions in order to conserve momentum
What is Pair Production
- When a photon is converted into a particle and antiparticle pair
- This can only occur when the photon has an energy greater than the total rest energy of both particles, any excess energy is converted into kinetic energy of the particles
