CHEM LESSON 1

• Democritus


  • Atomos - Building blocks of matter
  • The shape of an atom explain the elements behavior
• John Dalton


  Solid Sphere - Atom is solid indivisible sphere
• J.J Thomson


  Plum Pudding - Negative electrons are embedded in a sea of positive charges
• Ernest Rutherford


  Nuclear - Positive charges are located in central nucleus
• Niels Bohr


  Planetary - Electrons having circular orbits with different energy level
• Erwin Schrodinger


  • Quantum - Electrons are in the clouds
  • Less dense
• Electrons


  • Act like waves
  • Exact location cannot be determined
• Orbitals


  Region in an atom where there is a high probability of finding electrons
• Atomic Orbitals


  • s
  • p
  • d
  • f
• f orbitals


  • Most diffused shape
• Electron Configuration Notation


  Describes how electrons are distributed in atomic orbitals
• Principal Quantum Number


  Indicates the energy level or shell where an atomic orbital can be found
• Azimuthal Quantum Number


  Specifies the sublevel (or subshell) within a particular principal energy level
• Magnetic Quantum Number


  Indicates the specific orbital within the sublevel where the electron is found
• Spin Quantum number


  Pauli exclusion principle, only a maximum of two electrons can occupy an orbital, and they must have opposite spins to minimize repulsion between them
• Aufbau Principle


  Electrons fill the lowest energy orbitals first
• Hund's Rule


  • Atomic orbitals maximize the number of electrons with the same spin
  • Electrons will singly occupy each orbital and with parallel spins before they pair up
• Pauli Exclusion Principle


  Electrons will pair with opposite spins
• Octet Rule


  Atoms combine to form compounds and follow the noble gas configuration, a stable configuration
• Attaining stable configuration


  1. Transfer of electron/s: gaining or losing

  2. Sharing of electrons
• Valence Electrons


  The electrons involved in chemical bonding
• Lewis Structure


  • A dot is placed in each of the four sides of the element symbol before pairing with another as needed to represent all the valence electrons of the elements
  • There are no strict rules on which sides to pair up first so the dot symbol for oxygen may be written in several equivalent forms
• Lewis Electron Dot Structure (LED)


  • Used to illustrate how valence electrons participate in chemical bonding
  • The core/central element is represented by its chemical symbol
  • The valence electrons are represented by dots around the chemical symbol