matter waves - describes wave characteristics of material particles  

• all matter have wavelengths
• wavelength inversely proportional to mass/velocity
• l = Planck's constant / (mass x velocity) = h / mv
• microscopes use wave properties of electrons to map out surfaces

quantum (wave) mechanics - studies w/ subatomic particles  

• wave functions - mathematical functions describing electron's matter wave
  • represented by y, but has no physical meaning by itself
  • probability density = y2
  • electron density - areas w/ high probability of finding electrons
• orbital - describes distribution of electron density in space
  • not the same as the orbits mentioned in Bohr's model
  • path of electron can't be precisely tracked (due to uncertainty principle)
• quantum numbers - n, l, ml used to describe orbitals
  • n = positive integer, principle quantum number; increases as electron gets farther away from nucleus
  • En = (-2.18 x 10-18 J)(1/n2)
  • l = integer from 0 to n-1, azimuthal quantum number; describes orbital shape
  • ml = integers between l and -l, magnetic quantum number; describes orientation of orbital
• electron shell - collection of orbitals w/ same n value
• subshell - orbitals w/ same n and l values
• n subshells in the shell w/ principle quantum number n
• each subshell has 2(l)+1 number of orbitals
• n2 = total number of orbitals in a shell
• ground state - electron in lowest energy orbital
• excited state - electron in any other orbital, reaches this level by absorbing photons