Unit 1.7 - Particles and Nuclear Physics

• Atomic number = Number of protons
• The mass number is the total number of protons and neutrons.
• Mass number = Number of neutrons + number of protons
• Isotopes are atoms with different numbers of neutrons but the same atomic number.
• The nucleus is positively charged because it contains more positive charges than negative ones, so there must be an attractive force between the electrons and the nucleus to keep them together.
• Nuclides are nuclei that have the same atomic number, but may be different isotopes.
• Radioactive decay occurs when an unstable nucleus emits radiation to become more stable.
• A nuclide can be represented by its symbol (e.g., U-235) which shows the element's name followed by the mass number written as a superscript to the left of the chemical symbol.
• An atom has a neutral charge overall as the number of electrons equals the number of protons.
• Alpha particles consist of two protons and two neutrons bound together as a helium nucleus.
• Beta minus particles are high-energy electrons produced by beta minus decay.
• Gamma rays are photons of electromagnetic radiation emitted during nuclear decay.
• Hadrons feel the strong nuclear force
• Hadrons are made of quarks
• Hadrons can be split into two groups; baryons and mesons
• Baryons have three quarks (up, down, or strange ect)
• Mesons contain two quarks; one a quark and one an antiquark
• Protons and neutrons are both baryons
• Protons are the only stable baryons
• Neutrons are not stable baryons
• Antibaryons are made up of three antiquarks (up, down, or strange ect)
• Baryon number - the number of baryons present in a particle.
• Baryons count +1 towards the baryon number
• Antibaryons count -1 towards the baryon number
• Baryon numbers are quantum numbers (integers)
• In all interactions, the baryon number must be conserved