Elements/Quantum Numbers

• Atomic Number = number of protons
• Atomic Weight/Mass Number (A): number of protons and neutrons
• Isotopes: variation of the same element


  e.g. Chlorine

  Cl-35: P = 17, N = 18

  Cl-37: P = 17, N = 20
• Hydrogen Isotopes

  1. Protium: N = 0
  2. Deuterium: N = 1
  3. Tritium: N = 2
• Periods are horizontal, groups are vertical
• Main Energy Levels: fixed distances from the nucleus where we can find the electrons
• Magnetic Quantum Number (ml): no. of orbital
• Pauli Exclusion Principle: no more than two electrons can occupy the same orbital
• Quantum Numbers: set of numbers used to describe the position and energy of the electron
• Principal Quantum Number (n): same as period, distance of nucleus to the orbital
• Bohr Model: shows the specific orbital
• Azimuthal Quantum Numbers (l): describes the shape

  value = total number of angular nodes in an orbital
• Spin Quantum Number (Ms): indicates the direction of an electron's spin

  all electrons in the same sublevel should have different directions
• Aufbau Principle: fill the orbitals in order of increasing energy levels
• Hund's Rule: fill orbitals one at a time across an energy level before pairing electrons