CHEMISTRY L1

• J.J Thomson


  PLUM PUDDING

  • (1897)
  • Negative electrons are embedded in a sea of positive charges.
• Ernest Rutherford


  NUCLEAR

  • (1911)
  • Positive charges are located within a central nucleus.
• Niels Bohr


  PLANETARY

  • (1913)
  • Electrons are restricted in circular orbits with different energy levels.
• Erwin Schrödinger


  QUANTUM

  • (1926)
  • Electrons are in clouds surrounding the nucleus, and this cloud is less dense.
• ATOMIC ORBITALS


  • Electrons act like waves.
  • The exact location of electrons cannot be determined.
• Orbitals


  • A region in an atom where there is a high probability of finding electrons
  • Atomic orbitals (s, p, d, or f)
• ELECTRON CONFIGURATION NOTATION

  • describes how electrons are distributed in its atomic orbitals.

  A) type of orbital

  B) Energy level (n) value

  C) number of electrons in orbital

  
• TYPE OF ORBITAL

  A) 2

  B) 6

  C) 10

  D) 14

  
• PRINCIPAL


  • Distance of the electron from nucleus
  • It indicates the energy level or shell where an atomic orbital can be found.
• Azimuthal


  • Shape of the orbital
  • Specifies the sublevel (or subshell) within a particular principal energy level.
• MAGNETIC


  • Orientation of the orbital
  • Indicates the specific orbital within the sublevel where the electron is found.
• SPIN


  • Orientation of the electron spin
  • Pauli exclusion principle, only a maximum of two electrons can occupy an orbital, and they must have opposite spins to minimize repulsion between them.
• Rules for Orbital Diagram


  1. The lowest energy orbitals are filled before the higher energy orbitals
  2. Each orbital gets one electron first before a second electron is added to the orbital
  3. Only 2 electrons of opposite spins can occupy each orbital
• 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.

  There are two ways of attaining such stable configuration:

  1. transfer of electron/s: gaining or losing
  2. sharing of electrons
• Valence Electrons 


  • the electrons involved in chemical bonding
• Writing Lewis Structures

  • 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 it’s chemical symbol.
  • The core/central element is represented by it’s chemical symbol.
• Valence Electrons


  • represented by dots around the chemical symbol.