Do Now:

1. Do Now: 1. Ionization Energy is defined as the amount of energy required to ___________ an electron while Electron Affinity is the amount of energy change when at atom ____________ an electron. 2. Circle the element which is more likely to lose an electron (Hint: think lower Ionization Energy). Justify your choice citing the trend in a sentence. Sodium (Na) vs. Rubidium (Rb) _____________________________________________________________ 3. Circle the element which is more likely to gain an electron (Hint: think larger Electron Affinity). Justify your choice citing the trend in a sentence. Boron (B) vs. Fluorine (F) _________________________________________________________ lose gain Rubidium because ionization energy decreases down the group. Fluorine because electron affinity increases across the period.

2. Periodic Trends Unit 3 Lesson 4 Trend 4: Electronegativity

3. Objectives • SWBAT use the trends in Electronegativity to predict how strongly the atoms will attract the electrons in the bond.

4. Agenda • Defining Electronegativity • The Electronegativity Trend by Group • Why the Electronegativity Group Trend? Zeff • The Electronegativity Trend by Period • Why the Electronegativity Period Trend? Zeff • Independent Practice

5. Trend 4: Electronegativity (Definition) • How likely an atom is to attract electrons toward itself in a chemical bond. • Warm colors have a higher electron density • Cool colors have a lower electron density Linus Pauling (1901-1994) Came up with Electronegativity Won 2 Nobel Prizes

6. Comparison • Electronegativity – How likely is an atom to attract electrons toward itself in a bond. NH3 B(OH)3 • Electron Affinity – How likely an atom is to gain/steal an electron from another atom altogether. Measures energy specifically!

7. Electronegativity Trend by Group ? EN decreases

8. Electronegativity Trend by Group • Electronegativity decreases down the group. • Atoms are less likely to pull electrons toward them in a bond as they get larger.

9. Electronegativity Trend by Group Reason • Calcium because EN decreases down the group. • Neither! Noble Gases have n0 EN! Which has a higher EN? • Calcium (Ca) or Barium (Ba) • Sulfur (S) or Oxygen (O) • Neon (Ne) or Argon (Ar) • Bismuth (Bi) or Arsenic (As)

10. Why the EN Group Trend? Zeff 1. Atomic Radius Increases • As atomic radius increase, the valence electrons get further from the nucleus and are more weakly held (due to electron shielding). • Hence larger atoms aren’t pulling as hard on their valence electrons OR the electrons of neighboring atoms. 2. Electron Shielding Increases 3. Zeff Decreases 4. Atoms want electrons less 5. EN decreases

11. Agenda • Defining Electronegativity • The Electronegativity Trend by Group • Why the Electronegativity Group Trend? Zeff • The Electronegativity Trend by Period • Why the Electronegativity Period Trend? Zeff • Independent Practice

12. Electronegativity Trend by Period increases • Electronegativity ___________from left to right across the period. • Atoms are _____ likely to attract an electron. more EN increases ?

13. Electronegativity Trend by Period Reason • Oxygen because EN increases across the period. • Noble Gases are exceptions (0 EN) • EN increases across the period so B (group 13) has a higher EN than Li (group 2) Which has a higher 1st EN? • Oxygen (O) or Carbon (C) • Lithium (Li) or Neon (Ne) • Lithium (Li) or Boron (B) • Silicon (Si) or Sodium (Na)

14. Why the EN Group Trend? Zeff 4. Atoms want electrons more 3. Zeff Increases 5. EN Increases 1. Atomic Radius Decreases 2. Electron Shielding Stays the Same • As atomic radius decreases, the valence electrons get closer to the nucleus and are more tightly held (due to a higher Zeff). • Hence smaller atoms want electons more and EN increases.

15. Summary of the Electronegativity Trend EN Increases EN Decreases

16. Summary of Trends 1-4 I. E., E.A., EN Increases Atomic Radius Decreases I. E., E.A., EN Decrease Atomic Radius Increases

17. Independent Practice • Let’s see what you’ve learned.