1. The Periodic Table & Electron Configurations

2. Periodic Law – when the elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern
Groups/families – vertical columns
Periods – horizontal rows
7 periods & 18 groups

3. 1 18 2 16 17

4. Metals, Nonmetals and Semimetals
Mostly solid at RT (exception Hg)
Shiny, malleable, ductile
Good conductors
Nonmetals
Often gases at RT, sometimes liquid or solid
Not shiny
Poor conductors
Metalloids (semimetals)
Properties between metals and non-metals (so identity disputed)

5. Valence electrons
Valence electrons – electrons in the highest principal energy level that are an element’s outermost electrons
For H and He these are found in the 1s orbital
H has 1 valence electron
He has 2 valence electrons

6. Valence Electrons
Oxygen has 6 valence electrons in its n=2 orbitals (outermost)

7. Valence Electrons
Aluminum has 3 valence electrons in its n=3 orbitals (outermost)

8. Valence electrons
Valence electrons are where all the chemistry happens
These are the electrons that are involved in chemical reactions

9. Electron Configuration: Noble Gas Notation
What is the electron configuration of He?
1s2
This can also be written as: [He]
This is understood to mean: 1s2
Li = [He]2s1
Be = [He]2s2
B = [He]2s22p1 etc
Until [He] 2s22p6 = [Ne]

10. Write the configurations for the first 4 alkali metals using sublevel and noble gas notation
Element
Sublevel Notation
Noble Gas Notation Li Na K Rb

11. Write the configurations for the first 4 alkali metals using sublevel and noble gas notation
What pattern do you observe?
The configuration of the valence electrons is the same for all of them.
This accounts for the similar chemical behavior of the alkali metals
This also explains group chemistry
Element
Sublevel Notation
Noble Gas Notation Li
1s22s1
[He] 2s1 Na
1s22s22p63s1
[Ne] 3s1 K
1s22s22p63s23p64s1
[Ar] 4s1 Rb
1s22s22p63s23p64s23d104p65s1
[Kr] 5s1

12. Orbital Blocks
Electron configurations are the key to the structure of the PT
Each block is defined by a type of orbital

13. s-Block Alkali metals and alkaline earth metals
plus hydrogen and Helium
Valence electrons only in s orbitals
Two groups b/c max of 2 electrons

14. p-Block Groups 13-18 (except He)
No p sublevel in first principal energy level
Thus no p sublevel in period 1
6 groups because p orbitals in a level contain a max of 6 electrons

15. d-Block Groups 3-12 First d orbital is 3d
Up to 10 electrons so d block is 10 elements wide

16. f-Block Placed below main body of PT 28 elements
f sublevel contains up to 14 electrons so 14 elements wide
Lanthanides insert after Lanthanum
Actinides insert after Actinium
Adding electron to the f-block does not follow the nice rules we have for elements further up the periodic table