1. Trends & the Periodic Table

2. Ionization Energy
Amount of energy required to remove an electron from a gas-phase atom
First ionization energy or ionization energy = energy required to remove most loosely held valence electron

3. Trends in ionization energy
What do you think happens to the ionization energy as you go down a column of the periodic table?
As you go across a row?

4. 
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Valence electrons in both atoms feel an effective nuclear charge of +1, but the Cs valence electron is a lot farther away from the nucleus
The electrostatic attraction will be much weaker so it’s easier to steal the electron away from Cs
Source: Conceptual Chemistry by John Suchocki

5.  It’s easier to steal an electron from the Li than the Ne
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It’s easier to steal an electron from the Li than the Ne
Li has a smaller effective nuclear charge and the valence electron is a little farther away from the nucleus
Li has less “proton pulling power” than Ne
Source: Conceptual Chemistry by John Suchocki

6. Trends in ionization energy
Ionization energy decreases as you go down a column
it gets easier & easier to remove the valence electron
Ionization energy increases as you go across a row
it gets more difficult to remove the valence electron

7. Periodic properties: Graph shows a repetitive pattern
(Note: Doesn’t have to be a straight line)

8. Electronegativity
Relative ability of an atom to attract electrons in a bond
The noble gases tend not to form bonds, so they don’t have electronegativities
Unit = Pauling
Fluorine is the most electronegative element at 4.0 Paulings

9. Trends in electronegativity
Related to “proton pulling power”
Increases as you go across a row
Decreases as you go down a column
Remember: F is the most electronegative element!

11. Reactivity of Metals Metals are losers!
We judge the reactivity of metals by how easily they give up electrons
The most active metals are Cs and Fr
For metals, reactivity goes up as ionization energy goes down

12. Trends for Reactivity of Metals or Metallic Character
Increases as you go down
Easier to lose electrons!
Decreases as you go across
Harder to lose electrons!

13. Reactivity of Non-metals
Non-metals are winners!
We judge the reactivity of non-metals by how easily they gain electrons
The most active non-metal is fluorine
For non-metals, reactivity increases as electronegativity increases

14. Trend for Reactivity of Non-metals: Depends on “proton pulling power”
Increases as you go across
Decreases as you go down (Shielded by more inner-shell electrons)