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Electron configurations tells us in which orbitals the electrons for an element are located.

Electron Configurations. Electron configurations tells us in which orbitals the electrons for an element are located. Three rules: electrons fill orbitals starting with lowest n and moving upwards ( Aufbau Principle);

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Electron configurations tells us in which orbitals the electrons for an element are located.

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  1. Electron Configurations • Electron configurations tells us in which orbitals the electrons for an element are located. • Three rules: • electrons fill orbitals starting with lowest n and moving upwards (Aufbau Principle); • no two electrons can fill one orbital with the same spin (Pauli Exclusion Principle); • for orbitals within the same sub-level, electrons fill each orbital singly before any orbital gets a second electron (Hund’s rule). • There are a few exceptions which will be discussed later

  2. Information about orbitals • Orbitals with 1 e- in them are called bonding sites because they can be shared • Stability order: • 1st Order: Totally full or Totally empty energy level • 2nd Order: Totally ½ full energy level • 3rd Order: Part full, part ½ full & part empty level • OCTET RULE: When outer s & p orbitals are full, EXTREMELY STABLE • Filled d or f set of orbitals is EXTREMELY STABLE

  3. Orbital Filling Order • Filling order is taught this way in many schools.

  4. Example (Nitrogen; atomic number = 7) • Electron Configuration 1s2 2s2 2p3 • Noble Gas Configuration (shorthand) [He] 2s2 2p3 • Orbital Notation ____ ____ ____ ____ ____ 1s 2s 2p • Energy Level Diagram

  5. Nitrogen Example • How many electrons are present in an atom of nitrogen? • 7 electrons • How many completely filled orbitals are in an atom of nitrogen? • 2 (1s and 2s orbitals) • How many partially filled orbitals (bonding sites) are in one atom of nitrogen? • 3 (each 2p orbital)

  6. Nitrogen

  7. Elements Electron configuration Shorthand

  8. Elements Electron configuration Shorthand

  9. Elements Electron configuration Shorthand

  10. Octet Rule • To become the most stable, atoms want to have an octet (8) of electrons in the highest occupied energy level (s and p orbitals are full) • Atoms will lose or gain electrons to obtain an octet; ions are formed • When electrons are lost, the charge is positive • When electrons are gained, the charge is negative • Up to four electrons in the highest occupied energy level  loss of electrons (s and p orbitals are empty) • Four or more electrons in the highest occupied energy level  gain of electrons (s and p orbitals are full)

  11. Example • Sodium (Na) • Atomic Number= 11 • Electron Configuration • 1s22s22p63s1 • Number of bonding sites ( partially filled orbitals) = 1 • Number of electrons to be lost or gained= 1 • Ion Charge +1 (loss of one electron)

  12. Example • Aluminum (Al) • Atomic Number= 13 • Electron Configuration • 1s22s22p63s23p1 or [Ne]3p1 • Number of bonding sites ( partially filled orbitals) = 1 • Number of electrons to be lost or gained= 3 • Ion Charge +3 (loss of three electrons)

  13. Write the following for Zinc • Atomic Number= 30 • Electron Configuration 1s22s22p63s23p64s23d10 • Noble Gas Configuration (shorthand) [Ar]4s23d10 or [Ar] 3d10 4s2 • Orbital Notation ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ 1s2s 2p 3s 3p 4s 3d • Energy Level Diagram

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