Ch. 9: Atomic and Nuclear Phenomena Flashcards
Photoelectric Effect
The ejection of an electron from the surface of a metal in response to light
Threshold Frequency
Minimum light frequency necessary to eject an electron from a given metal
Work Function
Minimum energy necessary to eject an electron from a given metal. Value depends on the metal used and can be calculated by multiplying the threshold frequency by Planck’s constant. The greater the energy of the incident photon above the work function, the more kinetic energy the ejected electron can possess
Ejected electron current
The ejected electrons create a current; the magnitude of this current is proportional to the intensity of the incident beam of light
Bohr model of the atom
States that electron energy levels are stable and discrete, corresponding to specific orbits
Absorbing
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 diff between the orbits. 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 diff between the orbits
Absorption Spectra
May be impacted by small changes in molecular structure
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
Amt of energy that is released when nucleons (protons and neutrons) bind together. The more binding energy per nucleon released, the more stable the nucleus.
The 4 fundamental forces of nature
strong and weak nuclear force, which contribute to the stability of the nucleus, electrostatic forces, and gravitation
Mass defect
Diff 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
Fusion
Occurs when small nuclei combine into larger nuclei. Energy is released in both fusion and fission bc the nuclei formed in both processes are more stable than the starting nuclei
Fission
Occurs when large nucleus splits into smaller nuclei. Energy is released in both fusion and fission bc the nuclei formed in both processes are more stable than the starting nuclei
Radioactive decay
The loss of small particles from the nucleus
Alpha decay
Emission of an alpha particle, which is a helium nucleus
Beta negative decay
Decay of a neutron into a proton with emission of an electron and an antineutrino
Beta positive decay
Also called positron emission is the decay of a proton into a neutron, with emission of a positron and a neutrino
Gamma decay
Emission of a gamma ray, which converts a high energy nucleus into a more stable nucleus
Electron capture
Absorption of an electron from the inner shell that combines w a proton in the nucleus to form a neutron
Half life
Amt of time required for half of a sample of radioactive nuclei to decay
Exponential decay
Rate @ which radioactive nuclei decay is proportional to the number of nuclei that remain
