6.4 Flashcards
Unified Atomic Mass Unit
1/12 the mass of a carbon-12 atom.
Proton number
the number of protons inside the nucleus of a particular atom.
Nucleon number
the number of nucleons (protons and neutrons) inside the nucleus of a particular atom.
Isotopes
atoms of the same element which contain the same number of protons but varying numbers of neutrons.
Alpha particle scattering experiment
1908 Rutherford: Geiger and Marsden
vast majority empty space
most of mass in central nucleus
nucleus small positive charge
Strong nuclear force
acts between nucleons and holds the nucleus together against the electrostatic repulsion of protons
Nuclear diameter order
10^-14 m
How does the strong force vary with distance?
Repulsive force between nucleons for distance of separation up to e. 0.510^15 m
Attractive between distances of 310^-15 and 0.510^-15m
Beyond a separation of 310^-15m the force approaches zero
Fundamental particles
Particles that cannot be broken down into smaller components
Hadrons
Particles consisting of a combination of quarks to give a net zero or whole number charge (protons and neutrons)
Leptons
Electrons and Neutrinos
Quarks
Components of Hadrons, have a fractional electric charge. They are the fundamental particles
Neutrino
almost no mass, zero charge.
antimatter partner: anti-neutrino
Weak nuclear force
Felt by quarks and leptons.
Can change quarks from one type to another.
Can change leptons from one type to another.
Responsible for beta decay
Antiparticle
Particle of antimatter that has the same rest mass as its matter counterpart.
When charged has equal and opposite charge to matter counterpart.
Alpha particle
Two protons & two neutrons ejected from the nucleus during radioactive decay
Emitted due to high instability
Beta particle
High speed electron emitted from the nucleus during beta decay
Produced when a neutron turns into a proton
Gamma ray
Form of electromagnetic wave with wavelength between 10^-16 and 10^-9
Emitted during gamma decay
Beta-minus decay
Neutron in the nucleus breaks down into a proton under weak nuclear force, and a beta-minus particle and an anti neutrino are emitted
A beta-minus particle is an electron
Beta-plus decay
Proton in the nucleus breaks down into a neutron under the influence of the weak nuclear force, and a beta plus particle and a neutrino are emitted.
A beta-plus particle is a positron
Activity
The number of nuclear decays (gamma rays emitted) per unit time.
Activity of one decay a second is a becquerel (Bq)
Decay constant
The probability that an individual nucleus will decay per unit time.
A/N
Half life
The mean time taken for the activity of a source, or number of undecayed nuclei present, to halve.
Carbon dating
Technique used to determine the age of organic matter form the relative proportions of carbon-12 and carbon-14 isotopes that it contains.
Half life or carbon 14 used to relate number left to time passed
Annihilation
Process in which a particle and its antiparticle interact and their combined mass is converted to energy via E=mc^2
Pair production
Process of creating a particle-antiparticle pair from a high energy proton
Mass defect
Difference in mass between the mass of a nucleus and the total mass of its separate nucleons
Binding energy
Minimum energy required to separate the nucleus into its constituent parts
Induced nuclear fission
When a nucleus absorbs slow moving neutrons and the resulting unstable nucleus undergoes a fission reaction to split into two smaller nuclei and a small number of neutrons, releasing energy.
Chain reaction
Sequence of nuclear reactions produced when an induced nuclear fission reaction triggers more than one further fission reaction
Control rod
Rod that can be lowered into the core of a nuclear reactor, absorb neutrons and slow down the chain reaction.
Made of boron usually
Moderator
Substance used in a nuclear reactor which slows down neutrons so that they have a greater chance of being absorbed by the fission reaction’s nuclear fuel.0
Made of graphite usually
Binding energy
The energy per nucleon that each holds and can release when the binds between two nucleons is broken
Nuclear Fusion process
4 protons react, first in pairs then, to form one helium-4 nucleus, this also supplies 25 MeV of energy and 2 positrons, 2 neutrons and 2 gamma photons
Advantages of using fusion for power production
No radioactive waste products are formed by the fusion process
Virtually unlimited supply of raw materials (sea water contains deuterium)
