1. Periodic Trends

2. Periodic Trends 1. Atomic Radius 2. Ionization Energy
3. Electronegativity
4. Ionic Radius

3. Atomic Radius
The distance from the center of the nucleus to the outermost valence shell K Na Li Ar Ne

5. Atomic Radius Periodic Trend Down a group the atomic radius increases
Due to the added energy levels
Electron shielding: core e- block the attraction between the nucleus and the valence e-
Across a period it decreases
Due to increased nuclear charge without additional shielding pulls e- in tighter

7. Ionization Atoms have no (or neutral) charges Ions are charged
Charge is caused by adding or losing electrons
+ charge: loss of electrons
- charge: gain of electrons
Why does this occur?
Stability = full valence shell
© 1998 LOGAL

9. Ionization Energy
Ionization Energy: the energy required to remove an electron from the valence shell
Why would an electron be removed?
Periodic Trend (opposite atomic radii)
Down a group I.E. decreases
Due to distance from nucleus & electron shielding
Across a period it increases
Due to increased nuclear charge without additional shielding pulls e- in tighter

10. Ionization Energy He Ne Ar Li Na K Removal of core electron = BIG IE
“Bumps” in graph due to loss of electrons from stable electron configurations He Ne Ar Li Na K

12. Second and Third Ionization Energy
Second I. E.: the energy required to pull the second electron off the same atom
Third I.E.: the energy required to pull the third electron off the same atom
Would the 2nd & 3rd IE be greater or lesser than the 1st?

13. Electronegativity
Electronegativity: the ability of an atom to attract electrons in a chemical bond
Periodic Trend
Down a group the electronegativity decreases
Due to increasing atomic radii
Across a period it increases
Due to decreased atomic radii

16. Ionic Radius
The radius of a positive ion is smaller than the atomic radius of its neutral atom
Due to loss of electron and often energy level

17. Ionic Radius
The radius of a negative ion is larger than the atomic radius of its neutral atom
Due to electron repulsion
© 2002 Prentice-Hall, Inc.

18. Examples Which atom has the larger radii?
Be or Ba
Ca or Br
Which atom has the higher 1st I.E.?
N or Bi
Ba or Ne
Which particle has the larger radius?
S or S2-
Al or Al3+