1. 01/06/2016 ObjectiveDo Now Identify more group and period trends and explain why they occur. Explain why atoms decrease in size across periods (rows) of the Periodic Table even though there are more protons, neutrons, and electrons.

2. Reminders ●Tutoring is now available on Mondays after school. ●Quiz - Friday, January 8 - Periodic Families and Trends

3. Electron Shielding Shielding electrons "shield" the valence electrons from the force of attraction exerted by the positive charge in the nucleus.

4. Electron Shielding Shielding electrons "shield" the valence electrons from the force of attraction exerted by the positive charge in the nucleus. Electronegativity increases from bottom to top

6. Electronegativity increases from left to right

8. Interpolation

9. Calculating % Error 1)Accepted value - Experimental value = Experimental error 2) Experimental error X 100% = % Error Accepted value

10. Calculating % Error 1)Accepted value - Experimental value = Experimental error 2) Experimental error X 100% = % Error Accepted value Density of aluminum = 2.70 g/cm 3 Experimentally measured density = 2.68 g/cm 3

11. Calculating % Error 1)Accepted value - Experimental value = Experimental error 2) Experimental error X 100% = % Error Accepted value Density of aluminum = 2.70 g/cm 3 Experimentally measured density = 2.68 g/cm 3 2.70 g/cm 3 - 2.68 g/cm 3 X 100% = 0.74% 2.70 g/cm 3