Periodic Trends We will explain observed trends in  Atomic (and Ionic) Radius  Ionization Eenergy  Electronegativity size lose e – attract e – nuclear charge & shielding explained by: (protons) & (levels)

inner e – levels block nuclear charge down a group Nuclear Charge & Shielding shielding: nuclear charge:protons(+) attracting e – ’s(–) Li across a period Na Ne Ar What happens to atomic radius? decreases increases WHY?

Atomic Radius -more levels of shielding (less attraction) increases down group -more nuclear charge (more attraction) decreases across period

Cations from metals:  e – ’s removed  positive (+) charge  smaller  outer shell lost Anions from nonmetals:  e – ’s added  negative (–) charge  larger  more e – repulsions Ions & Ionic Radius

decreases down a group -more levels of shielding (less attraction) -more nuclear charge (more attraction) increases across period Ionization Energy (IE): energy required to remove an e – +

Electronegativity (EN) Trends atom’s ability to attract bonded electrons decreases down group increases across period -more levels of shielding (less attraction) -more nuclear charge (more attraction)

Periodic Trends (Summary) so…Atomic Radius __________ so…Electronegativity _________ so…Ionization Energy _________ so…Electronegativity _________ so…Ionization Energy _________so…Atomic Radius __________ nuclear charge shielding All explained by ATTRACTION: ATTRACTION INcreases ATTRACTION DEcreases decreases increases decreases increases

1. Atoms get ________ down a ________. A. bigger, period B. smaller, group C. bigger, group D. smaller, period Quick Quiz! WHY? more energy levels more shielding less attraction

2. Atomic radii _________ across a period? A. atoms get bigger B. atoms get smaller C. atoms stay the same size D. atoms WHY? more protons more nuclear charge more attraction Quick Quiz.

3.Which of the following correctly orders atomic size from largest to smallest? A. F > Cl > Br B. Li > Na > K C. F > N > B D. Mg > Al > S Quick Quiz.

4.Metals tend to ________ electrons to form _________ cations. A. gain, positive B. gain, negative C. lose, negative D. lose, positive Quick Quiz.

5.As you go across period 3 from Mg to Cl, the energy needed to remove an electron from an atom ______________. A. generally increases B. generally decreases C. does not change D. varies unpredictably. Quick Quiz. WHY? more protons more nuclear charge more attraction (same energy level/shielding)

6.Which of the following is the most electronegative? A. Cl B. Se C. Na D. I Quick Quiz.

7.The noble gases have _____________. A. high ionization energies. B. high electronegativities. C. large atomic radii. D. a tendency to form both cations and anions. Quick Quiz.

8.Alkali metals have lower ionization energies than halogens because _______________. A. alkali metals are smaller with more protons. B. halogens are larger with more protons. C.alkali metals are larger with lower nuclear charges. D. halogens are smaller with fewer protons. Quick Quiz.

9.Fluorine is the most electronegative halogen because it is ___________________. A. larger with more energy levels (shielding) B. smaller with more energy levels (shielding) C. smaller with fewer energy levels (shielding) D. larger with fewer energy levels (shielding) Quick Quiz.