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Introduction to Electronic Structure

Review of Atomic Physics

model of helium atom
Schematic of helium atom
  • Each atom has a number of electrons about the nucleus.
  • Energy levels of electrons in an atom are quantized (discrete levels)
  • Electron may be elevated to excited state by addition of energy
  • "Excited" electron can relax to lower level by emitting photon.
  • Example of emission spectrum: hydrogen; (from bluegiant.phys.ksu.edu)

Pauli Exclusion Principle

How do electrons "stack up" in the atom?

A particular atomic orbital has fixed values of n, l, and m and can thus contain a maximum of TWO electrons (one of each spin).

Building Elements

Each additional electron gives the electron "cloud" of the atom a much different behavior -- That is why each element is different.

Periodic Table

Examine an abridged Periodic Table
hydrogen: 1s1
helium: 1s2
lithium: 1s2, 2s1
beryllium: 1s2, 2s2
boron: 1s2, 2s2, 2p1
carbon: 1s2, 2s2, 2p2
nitrogen: 1s2, 2s2, 2p3
oxygen: 1s2, 2s2, 2p4
flourine: 1s2, 2s2, 2p5
neon: 1s2, 2s2, 2p6
sodium: [Ne] 3s1


Much of chemistry depends on how "filled" the shells are:

Group Activity

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Comments, suggestions, or requests to ghw@udel.edu.

Last updated Jan. 22, 1998.
Copyright George Watson, Univ. of Delaware, 1996.