(EL) - Energy, Matter and Modern Analytical Techniques

• Electromagnetic spectrum:

  • Shows types of radiation at different frequencies
  • Made up of radio waves, microwaves, and gamma rays
  • Energy increases from left to right
  • Atoms can release energy in the electromagnetic spectrum
• Line spectra:

  • Way of identifying elements
  • Evidence for energy levels in shells
  • Electrons can move between discrete energy levels
  • Absorb energy to move to higher energy levels
  • Emit energy when moving back to lower energy levels
• Emission spectra:

  • Shows frequency of light given out when an electron moves down energy levels
  • Different colored bands represent different frequencies
  • Unique to specific elements
  • Acts like a barcode for elements
• Absorption spectra:

  • Electrons absorb specific frequencies corresponding to energy gaps between shells
  • Dark bands on colored spectrum show absorbed frequencies
  • Electromagnetic radiation passed through element in gaseous state
• Line spectra energy levels:

  • Lines show electrons moving to different energy levels
  • Series of lines created when electrons move to the same energy level from different ones
  • Lines get closer together as energy and frequency increase
• Atomic emission spectra:

  • Electrons falling to ground state produce lines in ultraviolet part of the spectrum
  • Electrons falling to N=2 produce lines in visible part of the spectrum
  • Electrons falling to N=3 produce lines in infrared spectrum
  • Evidence for quantum shells in atoms
• Electrons can only exist in specific shells, defined as quantum levels, and cannot exist between them
• The energy gap between shells is measured in joules and is denoted as ΔE
• Planck's constant (H) is given in joules per Hertz and is used in the equation E = Hν to calculate energy and frequency
• Frequency (ν) is measured in Hertz or per second and is linked to the speed of light and wavelength
• The speed of light (c) is fixed at meters per second and is used to calculate frequency and wavelength
• To calculate the energy difference between shells, the frequency of light being absorbed or emitted is used along with Planck's constant
• Flame tests can be used to identify positive ions in solid samples based on the colors emitted when the sample is heated
• Colors emitted during flame tests:

  • Lithium: crimson
  • Sodium: yellowy orange
  • Potassium: lilac
  • Calcium: dark red
  • Barium: green
  • Copper: greeny blue
• Mass spectrometry is a spectral technique used to identify substances by analyzing the mass-to-charge ratio of ions
• Steps in mass spectrometry:

  • Sample vaporization
  • Ionization by high-energy electrons
  • Acceleration of positive ions through an electric field
  • Passage through an ion drift chamber
  • Detection of ions as electrical current
• Relative atomic mass is calculated by multiplying the abundance of each isotope by its mass-to-charge ratio and dividing by the total abundance
• Formula for relative atomic mass calculation:

  • (Abundance of isotope A * mass-to-charge of A) + (Abundance of isotope B * mass-to-charge of B) / Total abundance