Friday, October 2

Electron Configuration Notation

- Electron configuration notation eliminates the lines and arrows of orbital notation

- Instead, the number of electrons in a sublevel is shown by adding a superscript to the sublevel designation

- The helium configuration is represented by 1s²

- The superscript indicates that there are 2 electrons in helium’s 1s orbital

Elements of the Second Period

- In the first period elements, hydrogen and helium, electrons occupy the orbital of the first main energy level

- According to the Aufbau principle, after the 1s orbital is filled, the next electron occupies the s sublevel in the second main energy level

- The highest occupied energy level is the electron-containing main energy level with the highest principal quantum number

- The inner-shell electrons are electrons that are not in the highest occupied energy level

Elements of the Third Period

- After the outer octet is filled in neon, the next electron enters the s sublevel in the n=3 main energy level

- Noble Gas Notation

o The Group 18 elements (Helium, Neon, Argon, Krypton, Xenon, and Radon) are called noble gases

o A noble gas configuration refers to an outer pain energy level occupied, in most cases, by 8 electrons

o Ex. K-19 = [1s²2s²2p⁶3s²3p⁶]4s¹

- = [Ar]4s¹ ← complete electron configuration

o Remember, only noble gases can be placed in brackets

Orbital Box Diagrams

- Uses boxes, putting the correct arrows in the box

- Just like the line and arrow diagram

Elements of the Fourth Period

- The period begins by filling the 4s orbital, the empty orbital of lowest energy

- With the 4s sublevel filled, the 4p and 3d sublevels are the next available vacant orbitals

- The 3d sublevel is lower in energy than the 4p sublevel. Therefore, the five 3d orbitals are next to be filled

- Notable exceptions to this are Copper and Chromium