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Electron Rules. Unit 4 – The Electron. Electron Rules. Where do electrons go? There are 3 rules that govern…. Electron Rules. Aufbau Principle Electrons enter the lowest possible energy levels first Start with PEL PEL 1 has the lowest E, then 2,etc Then sublevels within a PEL
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Electron Rules Unit 4 – The Electron
Electron Rules • Where do electrons go? • There are 3 rules that govern…
Electron Rules • Aufbau Principle • Electrons enter the lowest possible energy levels first • Start with PEL • PEL 1 has the lowest E, then 2,etc • Then sublevels within a PEL • S is the lowest then p,d,f • Each orbital in a sublevel is equal in E
Electron Rules BUT • E- from very full PELs can spill into other PELs • Sometimes it takes less E to go to the next PEL
Electron Rules • Order of orbital filling – follow the arrow 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f
Electron Rules 2. Pauli Exclusion Principle • Maximum of 2e- per orbital • Must have opposite ‘spins’
Electron Rules 3. Hund’s Rule • In orbitals of equal E, e- fill orbitals one-by-one until they HAVE TO pair up! • Orbitals take 1 e- each with parallel spins, before doubling up • Example: 2p with 2e- Spread the electrons out With parallel spins as much as you Can before pairing
Electron Rules • Orbital Diagrams • Visual representation of electron orbital filling • Examples: • H 1s
Electron Rules • Examples: • He • Li • C 1s 1s 2s 2s 2p 1s
Electron Rules • Electron Configurations • Shorthand version of orbital diagrams # of e- in sublevel Principal Energy Level 1s2 Sublevel (orbital type)
Electron Rules • Examples: • H 1s1 • He 1s2 • Li 1s22s1 • C 1s22s22p2
Electron Rules • Noble Gas Abbreviations • Shorthand version of electron configurations • Example: • Ne electron configuration • 1s22s22p6 • Na electron configuration: • 1s22s22p63s1 • Na with Noble Gas Abbreviation: • [Ne] 3s1