1. Dmitri Mendeleev Arranged elements by increasing atomic mass
Predicted properties of missing elements
Episode 401

2. Henry Moseley Discovered that each element has a unique atomic number
Arranged elements by increasing atomic number
Now all the elements fit into place based on properties
Episode 401

3. Modern Periodic Law
Properties of elements repeat when elements are arranged by increasing atomic number
Periodic function or repeats
Episode 401

4. Questions about the extended periodic table:
Why do you think these elements get pulled out?
It makes the periodic table more compact.
Which element is in a different column than we are used to? He
What happens to the number of energy levels as you begin each new row?
Increases by 1
What is the similar characteristic in each column?
Electron distribution
Episode 401

5. Elements in the same column:
Have similar electron distributions
Have same number of valence electrons
Electrons lost, gained, or shared
Found in the s and p orbital of highest energy level
Have similar chemical properties
Ne:
1s2 2s2 2p6
Kr:
1s2 2s2 2p6 3s2 4s2 3d10 4p6
Episode 401

6. Noble Gases Have full outer energy level Have 8 valence electrons
Are stable
(inert or unreactive)
Episode 401

7. Using the periodic table to find electron distributions:
Episode 401

8. Noble Gas Configuration
Shorter way to do electron configurations using noble gases
Find noble gas on the end of row before the element and put its symbol in brackets.
Use diagonal rule to write the electron distribution for Sn (atomic # 50)
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p2
Use the noble gas distribution to write electron distribution for Sn
[Kr] 5s2 4d10 5p2
Episode 401

9. Noble Gas Configuration
Find noble gas on the end of row before the element and put its symbol in brackets.
Use diagonal rule to write the electron distribution for Fe (atomic # 26)
1s2 2s2 2p6 3s2 3p6 4s2 3d6
Use the noble gas distribution to write electron distribution for Fe
[Ar] 4s2 3d6
Episode 401