Colin Donnelly-
Photoelectric effect
The photoelectric effect is the ejection of an electron from the surface of a metal in response to light.
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Threshold frequency
The threshold frequency is the minimum light frequency necessary to eject an electron from a given metal.
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Work function
The work function is the minimum energy necessary to eject an electron from a given metal. Its value depends on the metal used and can be calculated by multiplying the threshold frequency by Planck’s constant.
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The greater the energy of the incident photon above the work function, ...
... the more kinetic energy the ejected electron can possess.
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The ejected electrons create a _____; the magnitude of this is proportional to _____.
current
the intensity of the incident beam of light
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Bohr model of the atom
Bohr model of the atom states that electron energy levels are stable and discrete, corresponding to specific orbits.
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Atomic 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.
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Atomic 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.
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Absorption spectra may be impacted by small changes in _____.
molecular structure
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Fluorescence
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.
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Nuclear binding energy
Nuclear binding energy is the amount of energy that is released when nucleons (protons and neutrons) bind together.
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The more binding energy per nucleon released, ...
... the more stable the nucleus.
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The four fundamental forces of nature are the _____ and _____, which contribute to the stability of the nucleus, _____, and _____.
strong and weak nuclear force
electrostatic forces
gravitation
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Mass defect
The mass defect is the difference between the mass of the unbonded nucleons and the mass of the bonded nucleons within the nucleus.
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The unbonded constituents have _____ and, therefore, _____ than the bonded constituents.
more energy
more mass
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The mass defect is the _____ during nuclear fusion.
amount of mass converted to energy
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Fusion
Fusion occurs when small nuclei combine into larger nuclei.
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Fission
Fission occurs when a large nucleus splits into smaller nuclei.
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Energy is usually _____ in both fusion and fission because the nuclei formed in both processes are _____ than the starting nuclei.
released
more stable
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Radioactive decay
Radioactive decay is the loss of small particles from the nucleus.
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Alpha (α) decay
Alpha (α) decay is the emission of an alpha particle, which is a helium nucleus.
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Beta-negative (β−) decay
Beta-negative (β−) decay is the decay of a neutron into a proton, with emission of an electron (e−, β−) and an antineutrino.
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Beta-positive (β+) decay
Beta-positive (β+) decay, also called positron emission, is the decay of a proton into a neutron, with emission of a positron (e+, β+) and a neutrino (ν).
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Gamma (γ) decay
Gamma (γ) decay is the emission of a gamma ray, which converts a high-energy nucleus into a more stable nucleus.
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Electron capture
Electron capture is the absorption of an electron from the inner shell that combines with a proton in the nucleus to form a neutron. This process also releases a neutrino from the nucleus.
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Half-life
Half-life is the amount of time required for half of a sample of radioactive nuclei to decay.
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Exponential decay
In exponential decay, the rate at which radioactive nuclei decay is proportional to the number of nuclei that remain.
