In the Clouds
Do you recognize this model? It’s the familiar “planetary” model of the atom. It’s often used as a symbol to represent the atom. It adequately represents the atom for some purposes. But scientific researchers need a more complex model of the atom.
Why It Matters
 Scientists use a quantum, or electron cloud, model of the atom. The quantum model is a mathematical model.

 The quantum model can’t give the exact locations of electrons. However, it can be used to determine their exact energy levels and explain chemical bonding. In other words, the quantum model can help scientists understand virtually every chemical change in the universe!
 Watch this video to better understand why quantum chemistry matters:
http://www.youtube.com/watch?v=aSBug7zfrRA
Can You Apply It?
At the links below, learn more about the quantum model of the atom. Then answer the questions that follow.
 http://www.rsc.org/chemsoc/visualelements/orbital/orbital_01.html
 http://www.cartage.org.lb/en/themes/sciences/chemistry/generalchemistry/atomic/electronicstructure/atomicstructure/Schrodinger/Schrodinger.htm
 http://www.nuffieldfoundation.org/practicalphysics/atom%E2%80%93quantummechanicalmodel
 What is quantum chemistry? Why is it important?
 The quantum atomic model doesn’t consider electrons to be like tiny planets in orbit around the atomic nucleus, as in the diagram above. What does the quantum chemist in the video consider electrons to be like?
 The quantum atomic model includes the idea of atomic orbitals. What is an atomic orbital?
 If an electron is in a particular orbital, what can you say conclusively about it?
 You can tell its energy level.
 You can describe its exact location.
 You can give the coordinates of its position.
 Two of the above
 A given orbital is indicated by a number and letter, such as 1s, 2p, or 3d. What do the number and letter represent?