1. ELECTRON
CONFIGURATION

2. HOW DO WE DESCRIBE THE LOCATION OF EACH ELECTRON IN AN ATOM?
WITH A SYMBOLIC NOTATION CALLED AN ELECTRON CONFIGURATION.

3. An Electron Configuration is a shorthand method of listing the location of the electrons in an atom. The system locates each electron by energy level and sublevel. The number of electrons in each sublevel is indicated with a superscript. For instance, the electronic configuration of Sodium is 1s22s22p63s1. This indicates that there are two electrons located in the 1s orbital, two electrons in the 2s orbital, six electrons in the 2p orbital and a single electron in the 3s orbital.

4. Remember:

5. RULES FOR PLACING ELECTRONS IN ORBITALS
1.  Aufbau Principle:  Electrons occupy lowest energy orbitals first.
2. The Pauli Exclusion Principle:  An orbital can hold a maximum of 2 electrons. No two electrons in an atom can have the same set of quantum numbers.
3.   Hund's Rule: when placing electrons into degenerate orbitals, there must be one electron in each orbital before any pairing of electrons can take place. {Degenerate orbitals are orbitals of the same energy level and sublevel.}

6. The Order Electrons Fill Orbitals

7. Electron Configuration of Zr
1s2
2s2
2p6
3s2
3p6
4s2
3d10
4p6
5s2
4d2

8. Core Notation of Sn
Locate Sn on the periodic table

9. Electron Configuration of Sn
Sn [Kr]
The noble gas core is Kr

10. Sn [Kr]5s2 The noble gas core is Kr
From Kr, go 2 spaces across the s-block in the 5th row  5s2

11. Sn [Kr]5s24d105p2 The noble gas core is Kr
From Kr, go 2 spaces across the s-block in the 5th row  5s2
Then go 10 spaces across the d-block on the 5th row  4d10
Finally go 2 spaces into the p-block on the 5th row  5p2

13. Orbital Diagram
Refer to a periodic table and write the electron configurations of these atoms. Write the orbital diagram for the orbitals not in the noble gas core. Zn I

14. Zn [Ar]4s23d10
I [Kr]5s24d105p5

15. Zn [Ar]4s23d10 I [Kr]5s24d105p5       4s 3d     