Chem Take out “Electron Address” to be stamped if you did not get it stamped last class Take out a Periodic Table (you’ll need one for today) Unit 4 Quest this Fri 11/2! Waves, Energy, Electrons

Aufbau Principle Under normal conditions, each electron occupies the lowest energy orbital available. http://www.iun.edu/~cpanhd/C101webnotes/modern-atomic-theory/aufbau-principle.html

Pauli Exclusion Principle Every electron spins; it can spin in one of two directions. An arrow pointing up (↑) indicates one direction. An arrow pointing down (↓) indicates the other direction. The Pauli exclusion principle states that a maximum of two electrons can occupy an orbital space, but only if they have opposing spins. OR RIGHT WRONG

Hund’s Rule WRONG RIGHT To minimize repulsion between electrons, Hund’s rule says that we put one electron in each orbital of the same energy before we add the second. p subshell WRONG RIGHT Room mate rule

Magnesium Mg 3p 3s 1s22s22p63s2 2p 2s 1s

Silicon Si 3p 3s 1s22s22p63s23p2 2p 2s 1s

Sulfur S 3p 3s 1s22s22p63s23p4 2p 2s 1s

Electron Configuration: 3 parts # electrons in orbital Energy Level Type of orbital

2 2 4

O 2 2 4 8

Electron Configuration Fill out the long form electron configuration first. We will do the Noble Gas Abbreviation and Valence Electron part after.

Valence Electrons The electrons in the outermost shell or highest energy level Valence electrons = total number of electrons in the highest s and p orbitals (must be of the same energy level)!

Noble Gases: Group 18 Have octet=full valence (outermost) shell All elements want to be a noble gas (so freaking bad). In other words, all elements want to have a full valence shell Remember: “8 IS GREAT!” Exception: helium: it only has 2 valence electrons

Electron Configurations can get very long! Abbreviated Electron Configuration for Be: Find the closest noble gas that comes before it [He] eliminates the need to write “1s2” [He] 2s2 2 valence electrons

[Ne] eliminates the need to write “1s22s22p6” Abbreviated Electron Configuration for Na: Find the closest noble gas that comes before it [Ne] eliminates the need to write “1s22s22p6” [Ne] 3s1 1 valence electron