2.  Knowing the position of electrons helps us with many topics:  Why chemical reactions occur  Why some atoms are more stable than others  Why some elements react with only certain atoms  Goal for this topic: We want to know how many electrons an atom has, and where they’re located.

3.  “Electron Cloud”  - Energy Levels ( 1 – 7)  - Sublevels (S,P,D,F – Shapes)  - Orbitals (Specific Pathways – X/Y/Z axis)

4. © 1998 by Harcourt Brace & Company s p d (n-1) f (n-2) 12345671234567 6767

5. Nucleus - S Sublevel – Think Sphere - P Sublevel – Figure 8 S Sublevel P Sublevel- X Axis P Sublevel- Y Axis P Sublevel- Z Axis

6.  Orbital Diagrams are Visual illustrations that show the order that electrons will follow as they fill in the electron cloud.  We start from the bottom and work your way up. That symbolizes starting on the first energy level and work outward.

7.  When filling in an orbital diagram, it’s important to follow three rules.  You need to know these by name and what each specifically says, so get ready to write them!

8.  Aufbau Principle  Electrons must fill the lowest sublevel available. (Letters - S,P,D,F)  You cannot skip any sublevels.  It’s like the Alphabet!

9.  Pauli Exclusion Principle  Each orbital (each box on the diagram) can hold only TWO electrons, and the electrons have opposite spins.

10. RIGHT WRONG  Hund’s Rule  Within a sublevel, place one electron in each orbital with the same spin before pairing them with a second electron. - “Empty Seat Rule”

11.  You are drawing arrows, and they represent electrons. (Neon has 10 electrons so you will need to draw 10 arrows.)  Divided up into different sublevels containing a specific number of orbitals. KNOW THIS INFO!  - The S sublevel has only 1 orbital= total of 2 e-  - The P sublevel has 3 orbitals = total of 6 e-  - The D sublevel has 5 orbitals = total of 10 e-  - The F sublevel has 7 orbitals = total of 14 e-

12. Fill in the orbital diagram for Magnesium

14. An atom’s electron configuration…  Describes the location of electrons within the atom  Identifies the shape of the electron clouds  - regions where the electrons are held.  Uses numbers and letters to describe electrons’ location and which electron cloud it is part of.

15. 1s 2 The “1” tells you how far from the nucleus the electrons can go. In this case, its in the 1 st energy level, which is the closest level to the nucleus. The “s” tells you the electron’s cloud shape. In this case it’s a spherically shaped cloud. It is called the s sublevel. Sublevel = Shape The “2” simply tells you how many electrons are in this cloud. In this case 2 electrons are creating the cloud. Note: Every orbital can only hold 2 electrons. They must have opposite spins.

16. O 8e -  Orbital Diagram zElectron Configuration 1s 2 2s 2 2p 4 1s 2s 2p

17.  Shorthand Configuration  This is a shorter way to do e - configurations Steps…  1) Write the symbol of the element you’re doing  2) Find the noble gas (group 8) that comes before the element you are doing.  3) To begin, put that noble gas in [brackets]  4) Starting with that noble gas, finish the electron configuration

18. zShorthand Configuration S 16e - Valence Electrons Core Electrons S16e - [Ne] 3s 2 3p 4 1s 2 2s 2 2p 6 3s 2 3p 4  Longhand Configuration

19. [Ar]4s 2 3d 10 4p 2  Example - Germanium

20.  LiNMg C 

21.  This will help  It is a way to remember the order in which electrons fill their orbitals. When you reach the far Left side, you reach a “wall” and must go back to The right hand side.