Atomic and nuclear Phenomena Flashcards
photoelectric effect
is the ejection of an electron form the surface of a metal in response to light.
Threshold frequency
the minimum light frequency necessary to eject an electron form a given metal. Work function is the minimum energy necessary to eject the electron from a given metal. value depends on metal and can be calculated. Greater the energy of the incident photon above the work function, the more kinetic energy the ejected electron can possess.
When electrons are ejected they 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 .
If and electron absorbs photon of light of the same frequency as the difference between orbits, it can
jump from a lower energy to higher energy orbit.
When an electron falls form a higher energy orbit
it emits a photon of light of the same frequency as the distance between orbits.
apsortioin spectra
may be impacted b 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 EM spectrum.
Nuclear4 binding energy
the amount of energy that is released when nucleons (protons and neutrons) bind together. The more binding energy per nucleon released, the more stable the nucleus.
What are 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
is the difference between the mass of the unbonded nucleons and the mass of the bonded nucleons within the nucleus. The unbounded constituents have more energy and, therefore, more mass than the bonded constituents. The mass defect is the amount of mass converged to energy during nuclear fusion.
fusion
occurs when small nuclei combine into larger nuclei
fission
occurs when a large nucleus splits into smaller nuclei
energy in fusion and fission
is released in both because 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 alpha particle which is a helium nucleus
A/Z X –> A-4/Z-2 Y + 4/2 a .
Beta-negative (B-) decay
the decay of a neutron into a proton, with emission of and electron (e-, B-) and antineutrino (v̅)
A/ZX –> A/Z+1 Y + B-
Beta positive (B+) decay or positron emission
the decay of a proton into a neutron, with emmission of a positron (e+, B+) and a neutrino (v)
A/Z X –> . A/Z-1 Y + B+
gamma (y) decay
the emission of a gamma ray, which converts a high -energy nucleus into a more stable nucleus
A/ZX* –> A/Z X +y
Electron capture
is the absorption of an electron from the inner shell that combines with a proton in the nucleus to form a neutron .
A/Z X + e- –> . A/Z-1 Y
Half life
the amount of time required for half of 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 .
energy of a photon light
E=hf
Max kinetic energy of an electron in the photoelectric effect
Kmax = hf-W
Work function
W=Hft .
Mass defect and energy
E = MC^2
nuclear decay (general form)
A/Z X –> A’/Z’ Y + emitted decay particle
Alpha decay
A/Z X –> A-4/Z-2 Y + 4/2 a .
Beta negative decay
A/ZX –> A/Z+1 Y + B-
rate of nuclear decay
Δn/Δt = -λn
Exponential decay
n = n0e^-λt
Decay constant
λ = ln2/T(1/2) = 0.693 T/ (1/2)
