1. Periodic Properties

2. Valence Electrons
Valence electrons – Electrons in the outer energy level that can be lost, gained, or shared (connected to the group #)
Group #
Valence e- 1 2 13 3 14 4 15 5 16 6 17 7 18 8

3. Atomic Radii
The atomic radius is a measure of the size of an atom (½ distance betw 2 nuclei).
The larger the radius, the larger is the atom.

4. Atomic Radii

5. Atomic Radii
Radii decrease across a period because the nucleus gets a larger positive charge
Radii increase down a group because the nucleus gets larger
Which is larger and why? Which is the smallest? Li, O, C, or F
Largest: Li Smallest: F
What about Be, Mg, Ca, or Sr?
Largest: Sr Smallest: Be

6. Ionization Energy Ion – an atom that has a positive or negative charge
Ionization – process that results in forming an ion
Ionization energy (IE) – energy required to remove one electron from a neutral atom (energy needed to make a positive charge)

7. Ionization Energy
A + Energy
A+ + e-
IE increases across a period because the nuclear charge increases (more electrons in the orbitals)
IE decreases down a group because it is easier to remove e- from higher energy levels

9. Electron Affinity
Electron Affinity (EA) – energy needed to add an electron to a neutral atom (opposite of IE).
A + e-
A- + energy

10. Electron Affinity EA decreases across periods (get more negative)
EA decreases down groups as nuclear charge increases.
***There are many exceptions to this rule!!!

11. Ionic Radii Cation – positive ion (decrease in atomic radii)
Anion – negative ion (increase in atomic radii)
Ionic radii decrease across periods because the electron cloud shrinks
Ionic radii increase down groups as energy levels increase

13. Electronegativity
Electronegativity -- the ability of an atom to attract electrons
Electronegativities increase across a period and decrease down groups (but there are exceptions!)
**Fluorine is the most electronegative atom!!

15. The Best Way to Remember….
Just know all the trends that surround Fluorine, and work your way down or across!
F – most electronegative, highest IE, lowest EA, small atomic and ionic radii

16. All Periodic Trends