1. Periodic Trends: 3. Ionization Energy 4. Electronegativity
What is ionization energy?
What is electronegativity?

2. IONIZATION ENERGY
Ionization Energy is energy needed to remove an outer valence electron.
1st IE energy required to remove 1st e-
2nd IE energy required to remove 2 e-
3rd IE energy required to remove 3 e-

3. Ionization Energy Before: Neutral Na Atom
After: 1st valence e- is removed
11p+
11 e-
Overall Net Charge = 0
Result:
11p+
10e-
Overall Net Charge = +1

4. What is the trend and why?
In groups = as you go down
WHY? Increased shielding effect,  distance between e- and nucleus
In rows = as you move across
WHY? Increased positive nuclear charge, as nucleus becomes more +,  nuclear charge, holds e- closer
More difficult to remove e- as they are located closer to nucleus.

5. What is the shielding effect?
Shielding of outer electrons by inner electrons
Prevents outer electrons from “feeling” effective nuclear charge

6. What is the shielding effect?

7. What is electronegativity?
Electronegativity is the ability of an atom to attract electrons
Used as a prediction of the type of bond that will form
FLOURINE is the MOST ELECTRONEGATIVE
CESIUM is the LEAST ELECTRONEGATIVE

8. What is the trend?

9. What is the periodic trend?
In groups = as you go down
WHY? Atom has higher number of energy levels, more inner electrons, less ability to attract e-
In rows = as you move across
WHY? Increased valence e- on outer energy level

10. TREND SUMMARY