This document discusses atomic structure and models of the atom. It describes Bohr's model of the atom from 1913 which represented electrons orbiting the nucleus in specific energy levels similar to planets orbiting the sun. It then introduces the electron cloud model which depicts electrons as existing in a probable "cloud" location around the nucleus rather than defined orbits, since their exact location cannot be known. The document also discusses electron configurations, ground states, and how atomic spectra provided evidence for Bohr's model.

7. Examples of Element Spectrum

10. Bohr Model of Lithium 3 4 e - e - e -

11. Bohr Model of Argon 18 22 18 Ar 39.948 e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e -

13. Electron Cloud Model