1. Periodic Trends
Chemistry I

2. What patterns can you find on the Periodic Table?
We have already discovered that
The Periodic Table is organized in order of increasing atomic number.
Elements in groups have similar physical and chemical properties.

3. Here are some important patterns (aka trends):
Atomic radius
Electronegativity
Ionization energy

4. Atomic Radius
distance from the center of an atom's nucleus to its outer most electron
Measured in picometers (10-12)

6. Electronegativity
The ability of an atom in a molecule to attract shared electrons to itself.
The Pauling scale measures elements from a scale of .7 to 4.0

8. Ionization Energy
The amount of energy required to pull the outer shell electron from an atom.
Example:
Na + energy --> Na+ + e-

10. What causes these patterns?
Shielding
Core charge

11. Shielding
The shielding of the outer shell electrons from its attraction to the nucleus
The inner levels of electrons do the shielding

12. Effective nuclear charge
The strength of the nucleus’ positive attraction for electrons
Core charge = proton charge + core electron charge
(core electrons are everything except for the valence electrons)