1. Periodic Trends

2. Electron attraction Electrons are attracted to protons –and repelled by electrons The closer an e - is to the nucleus, the more pull it feels The more p + in nucleus, the more pull it has The more e - are between an e - and the nucleus, the less pull it feels

3. Effective Charge (Z eff ) Actual pull that e- feels from the nucleus Increases across period –as more p + are pulling on same # of shells Decreases down group –as more shells are added –“shielding” increases

4. Periodic Trends All periodic trends can (should for IB test) be explained using –Shielding –Effective nuclear charge (Z eff ) –And/or “complete shells”

6. Reactivity

8. 2 nd Ionization Energy Energy required to remove second electron Which elements would be high? Low? Alkali metals Alkaline Earth Metals

9. Electronegativity tendency to attract electrons to itself (in a bond)

10. Ionic Radius

12. Practice Question... from May ‘05 IB Exam State and explain the trends in atomic radius and ionization energy for… The alkali metals from Li to Cs (4) The period 3 elements from Na to Ar (4) 1.Atomic radius increases and ionization energy decreases 2.As you go down a group, atoms have more shells 3.and the shielding effect increases so the shells feel less pull from the nucleus 4.As the pull decreases, e are held more loosely and are easier to remove 1.Atomic radius decreases and ionization energy increases 2.As you go across a period, electrons are added to the same shell 3.Protons are also added which increases the effective nuclear charge 4.As the pull increases, e are held more tighter and are harder to remove

13. My Favorite PT Site