7. Atomic and Nuclear Physics Flashcards
Photon
a discrete unit or package of light energy
Nuclide
a particular type of nucleus with a certain number of protons and neutrons
Isotope
nuclei with the same number of protons (Z) but different number of neutrons (N)
Nucleon
a proton or neutron
Nucleon Number (Mass Number) (A)
number of nucleons
Proton Number (Atomic Number) (Z)
number of protons in nucleus
Neutron Number (N)
number of neutrons in nucleus (N = A – Z)
Coulomb interaction (Coulomb force, electrostatic force)
electrostatic force of repulsion between the protons in the nucleus
Radioactive Decay
when an unstable nucleus emits a particle (alpha, beta, gamma)
- random
- spontaneous
Alpha Particle (α)
helium nucleus (2 protons + 2 neutrons)
Beta Positive Particle (β+)
electron
Beta Negative Particle (β-)
positron (antielectron)
Gamma Radiation (γ)
high energy (high frequency) electromagnetic radiation
Radioactive Half-life (T1/2)
a. the time taken for ½ the number of radioactive nuclei in sample to decay
b. the time taken for the activity of a sample to decrease to ½ its initial value
Artificial (Induced) Transmutation
when a nucleus is bombarded with a nucleon, an alpha particle or another small nucleus, resulting in a nuclide with a different proton number (a different element)
Unified Atomic Mass Unit
1/12th the mass of a carbon-12 nucleus
Mass Defect
difference between the mass of the nucleus and the sum of the masses of its individual nucleons
Binding Energy
energy released when a nuclide is assembled from its individual components (OR: energy required when nucleus is separated into its individual components)
Binding Energy per Nucleon
energy released per nucleon when a nuclide is assembled from its individual components
Nuclear Fission
a heavy nucleus splits into two smaller nuclei of roughly equal mass
Nuclear Fusion
two light nuclei join to form a heavier - source of the suns energy
Photoelectric Effect
the emission of electrons from a metal when electromagnetic radiation of high enough frequency falls on the surface
Threshold Frequency (f0)
minimum frequency of light needed to eject electrons from a metal surface
Work Function (Φ)
minimum energy needed to eject electrons from the surface of a metal
Millikan’s Stopping Potential Experiment
an experiment utilizing reverse voltage raised to such a level (stopping potential Vs) that it stops all emitted photoelectrons
de Broglie Hypothesis
All particles can behave like waves whose wavelength is given by λ = h/p where h is Planck’s constant and p is the momentum of the particle.
Matter Waves
All moving particles have a “matter wave” associated with them whose wavelength is the de Broglie wavelength.
Wave-Particle Duality
Both matter and radiation have a dual nature. They exhibit both particle and wave properties.
- Bainbridge Mass Spectrometer
a device used to determine atomic masses – consists primarily of a velocity selector and a magnetic chamber
Radioactive Decay Law
The rate at which radioactive nuclei in a sample decay (the activity) is proportional to the number of radioactive nuclei present in the sample at any one time. (A = λN)
Decay Constant (λ)
a. constant of proportionality between the decay rate (activity) and the number of radioactive nuclei present
b. probability of decay of a particular nuclei per unit time
Activity (A)
number of radioactive disintegrations (decays) per unit time
