WAVE BEHAVIOR OF MATTER

• The de Broglie Hypothesis

  • in 1924, de Broglie suggested that if waves of wavelength were associated with particles of momentum, then it should work the other way around
  • p=mv
  • p=h/ƛ
• Uncertainty Principle

  • by Werner Heisenberg
  • “It is inherently impossible for us to know simultaneously both the exact momentum and exact location of an electron in space”
• Uncertainty Principle

  • by Werner Heisenberg
  • “It is inherently impossible for us to know simultaneously both the exact momentum and exact location of an electron in space”

  
• Quantum Mechanical Model of Atoms

  • utilization of wave nature of objects on the atomic scale
• Basic Postulates of the Quantum Theory

  1. Atoms can exist only in certain energy states (level)
  2. in each energy state, the atom has a definite energy
  3. Atoms emit or absorb radiation (light) as they change their energy states
  4. E = hv =hc/λ
  5. The allowed energy levels of electrons in an atom (the energy states) can be described by sets of numbers called quantum numbers.
• Quantum Numbers and Atomic Orbitals

  • an atomic orbital is specified by four quantum numbers
• Principal Quantum Number

  • referred as n
  • a positive integer
• Angular Momentum Quantum Number

  • referred as l
  • an integer from 0 to (n-1)
• Magnetic Momentum Quantum Number

  • referred as ml
• Spin Quantum Number

  • referred as ms
  • could be -1/2 or +1/2
• Pauli's Exclusion Principle

  • formulated by Wolfgang Pauli in 1925
  • states that no two electrons in an atom can have the same set of 4 quantum numbers
  • ONLY 2 electrons per orbital
• Hund's Rule of Maximum Multiplicity

  • orbitals are occupied first by electrons possessing ms=+1/2 before electrons with ms=-1/2
  • this increases the stability of orbitals
• Aufbau Principle

  • orbitals are filled starting from the orbital of the lowest energy to the orbital with the highest energy
  • the larger n and l, the higher the energy