Atomic and Nuclear Phenomena (9)

Photoelectric Effect

is the ejection of an electron from the surface of a metal in response to light

Threshold Frequency

is the minimum light frequency necessary to eject an electron from a given metal

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 of frequency by Planck’s constant

More

the greater the energy of the incident photon above the work function, the ________ kinetic energy the ejected electron can possess

Current

the ejected electrons create this; the magnitude of this 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 _______ a photon of light of the same frequency as the energy difference between the orbits

Emits

when an electron falls from a higher-energy to a lower-energy orbit, it _________ a photon of light of the same frequency as the energy difference 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

is the amount of energy that is released when nucleons (protons and neutrons) bind together

More

the more binding energy per nucleon released, the _______ stable the nucleus

Strong and Weak Nuclear Force, Electrostatic Forces, and Gravitation

the four fundamental forces of nature are:

Strong and Weak Nuclear Force

contribute to the stability of the nucleus

Mass Defect

is 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. This is the amount of mass converted to energy during nuclear fusion

Fusion

occurs when small nuclei combine into larger nuclei

Fission

occurs when a large nucleus splits into smaller nuclei

Released

energy is _________ in both fusion and fission because the nuclei formed in both processes are more stable than the starting nuclei

Radioactive Decay

is the loss of small particles from the nucleus

Alpha Decay

is the emission of an alpha particle (alpha, 4 2 alpha, 4 2 He), which is a helium nucleus

Beta-negative Decay (Positron Emission)

is the decay of a proton into a neutron, with emission of a positron (e^+, beta^+) and a neutrino (v)

Gamma Decay

is the emission of a gamma ray, which converts a high-energy nucleus into a more stable nucleus

Electron Capture

is the absorption of an electron from the inner shell that combines with a proton in the nucleus to form a neutron

Half-life

is the amount of time required for half a sample of radioactive nuclei to decay

Exponential Decay

the rate at which radioactive nuclei decay is proportional to the number of nuclei that remain