Electronic Structure

• According to Democritus, the world is made up of tiny indivisible particles called atomos.
• In 1803, John Dalton proposed the solid sphere of an atom.
• In 1897, Joseph John Thomson (JJ Thomson) discovered the electron and made the plum pudding model.
• In 1911, Ernest Rutherford discovered the nucles and proposed the nuclear model.
• In 1913, Niels Bohr discovered orbits.
• Orbits are also known as energy levels (n).
• Ground state is the original orbit of the electron
• Excited state is the highest atomic orbit.
• In 1924, Louis de Broglie made the quantum mechanical model and developed the wave-particle duality.
• S < 2

  P < 6

  D < 10

  F < 14
• Principal Quantum Number (n)

  • Refers to the distance of the electrons from the nucleus
  • Known as the shell
  • Computed by 2n^2.
• Azimuthal Quantum Number (l)

  • Refers to the shape of the atomic orbit.
  • Computed by n - 1.
• Magnetic Quantum Number (ml)

  • The number of orbitals in a subshell.
  • The values are from -l to +l.
• Electron Spin Quantum Number (ms)

  • Indicates the spin of the electron.
  • -1/2 (counterclockwise) or +1/2 only (clockwise).
• Electron Configuration - shows how the electrons are distributed in an atom.
• Aufbau Principle

  • Must be filled from the lowest energy to the highest energy level.
• Hund's Rule

  • Must be filled singly before being paired.
• Pauli's Exclusion Principle

  • No 2 electrons can have the same set of quantum numbers.
• Chemical Bond - is the force of attraction that holds 2 atoms together.
• Chemistry is the study of matter.
• Law of Conservation of Mass

  • Proposed by Antoine Lavoisier.
  • States that matter is neither created nor destroyed
• Law of Definite Composition/Proportions

  • Proposed by Joseph Proust
  • A compound is made up of the same proportions of each element.
• Law of Multiple Proportions

  • Proposed by John Dalton
  • When 2 elements combine to form two or more compounds.
• Lewis Electron Dot Symbol

  • A method to represent valence electrons of elements.
• Noble Gases

  • The most stable atoms
  • Doesn't form chemical bonds with other atoms.
• Octet Rule

  • States that an element must lose, gain, or share 8 electrons in its valence shell during chemical bonding.