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

2. Periodic Trends

3. Background image: http://www.ul.ie/~slc/Pictures/periodic%20table.jpg Atomic Radius

4. 1. 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

5. Background image: http://www.ul.ie/~slc/Pictures/periodic%20table.jpg Electronegativity

6. 2. 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

7. Background image: http://www.ul.ie/~slc/Pictures/periodic%20table.jpg Ionization Potential

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

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

10. Background image: http://www.ul.ie/~slc/Pictures/periodic%20table.jpg Ionic Radius

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

12. 5. Metallic Properties Across Period MP DECREASES Down Group MP INCREASES