Atomic and Nuclear Phenomena Flashcards
the ejection of an electron from the surface of a metal in response to light
photoelectric effect
the minimum light frequency necessary to eject an electron from a given material
threshold frequency (ƒ(T))
light quanta that are present in an integral number in a light beam; have energy proportional to frequency of light
photons
relationship of energy to frequency of light:
E = hƒ
where:
E = energy of photon of light
h = Planck’s constant (6.626x10^-34 J*s)
ƒ = frequency of light
maximum kinetic energy of ejected electron:
K(max) = hƒ - W
where:
h = Planck’s constant (6.626x10^-34 J*s)
ƒ = frequency of light
W = work function of metal in question
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
work function
work function:
W = h ƒ(T)
where:
h = Planck’s constant (6.626x10^-34 J*s)
ƒ(T) = threshold frequency
states that electron energy levels are stable and discrete, corresponding to specific orbits
Bohr model of the atom
an electron can jump form a lower-energy to a higher-energy orbit by ____ a photon of light of the same frequency as the energy difference between the orbits
atomic absorption (absorbing)
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
atomic emission (emits)
may be impacted by small changes in molecular structure
absorption spectra
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
fluorescence
the amount of energy that is released when nucleons (protons and neutrons) bind together
nuclear binding energy
the strong and weak nuclear forces (which contribute to the stability of the nucleus), electrostatic forces, and gravitational forces
four fundamental forces of nature
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; is the amount of mass converted to energy during nuclear fission
mass defect
equivalence of matter and energy:
E = mc^2
where:
E = energy
m = mass
c = speed of light (3x10^8 m/s)
isotopic notation
elements are preceded by their atomic number (Z) as a subscript and mass number (A) as a superscript
where:
X = element
A = mass number (corresponds to number of protons plus number of neutrons)
Z = atomic number (corresponds to number of protons)
occurs when small nuclei combine into larger nuclei; energy is released because nuclei formed is more stable than starting nuclei
fusion
occurs when a large nucleus splits into smaller nuclei; energy is released because nuclei formed is more stable than starting nuclei
fission
the loss of small particles from the nucleus; naturally occurring spontaneous decay of certain nuclei accompanied by the emission of specific particles
radioactive decay
radioactive decay:
represent nuclear isotopes; parent nucleus __ undergoes nuclear decay to form a daughter nucleus __; sum of atomic numbers and mass numbers must be same on both sides of equation
X and Y
radioactive decay:
generic balanced equation:
radioactive decay:
the emission of an ____ particle, which is a He nucleus that consists of two protons, two neutrons, and zero electrons
alpha (α) decay
radioactive decay:
alpha (α) decay balanced equation:
radioactive decay:
the decay of a neutron into a proton, with emission of an electron (e-, __) (Z = -1, A = 0)
beta-negative (β-) decay
radioactive decay:
beta-negative (β-) decay balanced equation:
radioactive decay:
the decay of a proton into a neutron, with emission of a positron (e+, __) (Z = +1, A = 0)
beta-positive (β+) decay
has the mass of an electron but carries a positive charge
positron (e+, β+)
radioactive decay:
beta-positive (β+) decay balanced equation:
radioactive decay:
the emission of a ____ ray (a high-energy (high-frequency) photon), which converts a high-energy nucleus into a more stable nucleus; carry no charge and simply lower the energy of the parent nucleus without changing the mass number or atomic number
gamma (𝛾) decay
radioactive decay:
gamma (𝛾) decay balanced equation:
radioactive decay:
the absorption of an electron from the inner shell that combines with a proton in the nucleus to form a neutron; can be thought of as reverse of beta-negative (β-) decay
electron capture
radioactive decay:
electron capture balanced equation:
the amount of time required for half of a sample of radioactive nuclei to decay
half-life (T(1/2))
how the number of radioactive nuclei changes with time; the rate at which radioactive nuclei decay is proportional to the number of nuclei that remain
exponential decay
rate at which nuclei decay:
∆N/∆t = -λn
where:
∆N/∆t = rate at which nuclei decay
λ = decay constant
n = number of radioactive nuclei that have not yet decayed
exponential decay:
n = n(o) e^-λt
where:
n = number of radioactive nuclei that have not yet decayed
n(o) = number of undecayed nuclei at time t = 0
λ = decay constant
t = time
decay constant relation to half-life:
λ = ln 2 / T(1/2) = .693 / T(1/2)
where:
λ = decay constant
T(1/2) = half-life
