1. Periodic Table and Periodicity

2. Dmitri Mendeleev
“The elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties.”

3. I. History A. Dimitri Mendeleev, 1869 B. Moseley, 1914
periodic law: The chemical and physical properties of the elements are periodic functions of their atomic numbers; When the elements are arranged in order of increasing atomic number, there is a periodic repetition of their properties.

4. II. Structure/Organization
A. Periodic table
Periods
Groups or families
Valence electrons
- Representative elements
B. Metals
- Alkali metals
- Alkaline earth metals
- Transition metals
- Inner transition metals
C. Nonmetals
- Halogens
- Noble gases
D. Semimetals/metalloids

5. Compare properties of metals and nonmetals

6. Periodicity in properties
A. Ionization energy

7. Ionization Potential/Energy
IE: Energy required to remove e-
Higher the IE: more difficult to remove e-
Across Period
IE INCREASES*
* with each subshell
Why?
Down Group
IE DECREASES

8. B. Electronegativity

9. Electronegativity The ability to attract e- Across Period EN INCREASES
Because nuclear charge (# p+) increases
Down Group
EN DECREASES
Because more n, more shielding, e- further away from nucleus

10. C. Atomic/ionic radius

11. Atomic Radius Across Period Atomic size DECREASES
Because nuclear charge (# p+) increases, as e- are added to same n, pulls e- in tighter
Down Group
Atomic size INCREASES
Because more n (shells), more shielding,
e- further away from nucleus

12. Ionic

13. Ionic Radius Ion- Charged atom Cation
Positive (+) ion (neutral atom looses e-)
Anion
Negative (-) ion (neutral atom gains e-)

14. Ionic Radius Across Period IR DECREASES*
* with jump up in metalloids
Down Group
IR INCREASES
Compare to neutral atom Ex. Br
Valence e- are the outermost e- of an atom

15. D. Metallic character/nonmetallic character
Nonmetallic character increases
Metallic
Character
Increases

16. Metallic Properties
Across Period MP DECREASES Down Group MP INCREASES

17. Summary of Periodic Table Trends
Moving Left --> Right
Atomic Radius Decreases
Ionization Energy Increases
Electronegativity Increases
Metallic character decreases
Moving Top --> Bottom
Atomic Radius Increases
Ionization Energy Decreases
Electronegativity Decreases
Metallic character increases