Physics and Math 9 Atomic and Nuclear Phenomena

Physics and Math 9: Atomic and Nuclear Phenomena The Photoelectric Effect The ejection of an electron from the surface of a metal in response to light Energy of a photon of light: 𝐸 =ℎ$𝑓 7 𝑐 =speed of light= 3 × 106 To calculate l from 𝑓 use: 𝑐 =𝑓$l 8 Maximum kinetic energy in the photoelectric effect: 𝐾7:;= ℎ$𝑓 −𝑊 Threshold The minimum light frequency necessary to eject an electron Frequency: from a given metal. Work The minimum energy necessary to eject an electron from a Function: given metal. $$ℎ=Planck D sconstant=6.626$×$ 10HIJ$J$s 𝑊 =ℎ$𝑓 > $ Absorption and Emission of Light Bohr Model: States that electron energy levels are stable and discrete, corresponding to specific orbits. Absorption: An electron can jump from a lower-energy to a higher energy orbit by absorbing a photon of light of the same frequency as the energy difference between the orbits. Emission: When an electron falls from a higher-energy to a lower energy orbit, it emits a photon of light of the same frequency as the energy difference between the orbits. Absorption May be impacted by small changes in molecular structure. Spectra: Fluorescence: Occurs when a species absorbs high-frequency light and then returns to its ground state in multiple steps. Each step has less energy than the absorbed light and is within the visible range of the electromagnetic spectrum. Nuclear Binding Energy and Mass Defect Nuclear Binding Is the amount of energy that is released when nucleons Energy: (protons and neutrons) bind together. 4 Fundamental Strong and weak nuclear force, electrostatic forces, Forces of Nature: gravitation. Mass Defect: The difference between the mass of the unbonded nucleons and the mass of the bonded nucleons within the nucleus. The unbonded constituents have more energy and, therefore, more mass than the bonded constituents. The mass defect is the amount of mass converted to energy during nuclear fusion. Nuclear Reactions Fusion: Occurs when small nuclei combine into larger nuclei. Fission: Occurs when a large nucleus splits into smaller nuclei. Energy is released in both fusion and fission because the nuclei formed in both processes are more stable than the starting nuclei. Radioactive The loss of small particles from the nucleus. Decay: Mass N H J a N L b b LM HO LO Charge N g N J Alpha (a ) The emission of an alpha particle (a, JM a, M He), which is a Decay: helium nucleus. R X →$RHJ Y+$ J a S SHM LM Beta-negative The decay of a neutron into a proton, with emission of an (b -) Decay: electron (e-, b-) and an antineutrino (𝑣Y). H R R X→ SLO Y+ NHOb S Beta-positive “Positron emission”, the decay of a proton into a neutron, (b +) Decay: with emission of a positron (e+, b+) and a neutrino ( 𝑣). L R R X→ SHO Y+ NLO b S Gamma (g) The emission of a gamma ray, made up of photons, which Decay: converts a high-energy nucleus into a more stable nucleus. R ∗ X →SRX+NN g S Electron Is the absorption of an electron from the inner shell that Capture: combines with a proton in the nucleus to form a neutron. R R X+eH → SHO Y S Half-Life: The amount of time required for half of a sample of radioactive nuclei to decay. Or, the time it takes to reduce the radioactivity of a substance by half. Exponential The rate at which radioactive nuclei decay is proportional to Decay: the number of nuclei that remain. 𝑛=𝑛N $𝑒H l $] 𝑛=#$of$undecayed$nuclei 𝑛N =#$of$undecayed$nuclei$at$𝑡=0 l $=$known$decay$constant Note: If the problem just says “beta”, they mean “beta negative”. Beta-negative is the default.