1 / 25

Chemical Bonding

Chemical Bonding. How compounds are held together. Review Questions. When representing a water molecule as H-O-H, what do the lines represent? Write e - configs for argon, chlorine, neon, and sodium Ar = 1s 2 2s 2 2p 6 3s 2 3p 6 Cl = 1s 2 2s 2 2p 6 3s 2 3p 5 Ne = 1s 2 2s 2 2p 6

ferrol
Download Presentation

Chemical Bonding

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chemical Bonding • How compounds are held together

  2. Review Questions • When representing a water molecule as H-O-H, what do the lines represent? • Write e- configs for argon, chlorine, neon, and sodium • Ar = 1s2 2s2 2p6 3s2 3p6 • Cl = 1s2 2s2 2p6 3s2 3p5 • Ne = 1s2 2s2 2p6 • Na = 1s2 2s2 2p6 3s1 • Why is the phrase “sodium chloride molecule” incorrect?

  3. Objectives • Learn about ionic and covalent bonds and explain how they are formed • Learn about polar covalent bonds • Understand nature of bonds and their relationships to electronegativity • Understand bond polarity and how it is related to molecular polarity

  4. What is a BOND??? • Force holding two or more atoms together • Makes atoms function as a unit • Strength of the force = energy required to break bond = bond energy

  5. Types of bonding • Focus on two types of chemical bonds: • IONIC BONDING • COVALENT BONDING

  6. Ionic Bonding • Oppositely charged ions - strong bonding force • Electron is transferred to another atom • Metal + NonMetal • e- from Na transferred to Cl.  • Na atom stable (“looks” like Ne) • Cl is stable (“looks” like Ar)

  7. Covalent Bonds • Atoms share e- • 2 Cl atoms share e- • Both Cl stable (both “look” like Ar) • Occurs between non-metallic atoms

  8. Polar Covalent Bond • Sometimes, there is an unequal sharing of the electrons • Known as Polar Covalent bond. • Partial charge on atoms shown using lower case greek letter delta ∂

  9. Questions • What is meant by the term chemical bond? What subatomic particles are most important in bonds? • How are ionic bonds and covalent bonds different? • How is a polar covalent bond different from a covalent bond?

  10. Objectives • Learn about ionic and covalent bonds and explain how they are formed • Learn about polar covalent bonds • Understand nature of bonds and their relationships to electronegativity • Understand bond polarity and how it is related to molecular polarity

  11. Nature of bonds

  12. Electronegativity • Ability of atom in molecule to attract shared e- to itself • Increases going left to right across periodic table • Decreases going down a group

  13. Electronegativity • Range: Fluorine 4.0...Francium & Cesium 0.7 • Effect: Higher electronegativity of an atom, the closer shared e- will be to that atom when it forms a bond

  14. Electronegativity

  15. Bond Polarity • Bond Polarity depends on differencein electronegativity values of atoms forming bond • Atoms with very different electronegativities form very polar bonds • Ionic bonds areextreme case of bond polarity • Electronegativity difference greater than 2.0 considered ionic bond

  16. Bond Polarity Continuum

  17. Thinking question... • How do electronegativity trends compare to trends of atomic size?

  18. Problem • Arrange the following bonds in order of increasing polarity: H-H, O-H, Cl-H, S-H, F-H • H-H (2.1 - 2.1 = 0.0) • S-H (2.5 - 2.1 = 0.4) • Cl-H (3.0 - 2.1 = 0.9) • O-H (3.5 - 2.1 = 1.4) • F-H (4.0 - 2.1 = 1.9)

  19. Problems • For each of the following bond pairs, choose the one that is most polar • H-P & H-C • (2.1 - 2.1) < (2.5 - 2.1) • H-C • O-F & O-Cl • (4.0 - 3.5) = (3.5 - 3.0) • same • N-O & S-O • (3.5 - 3.0) < (3.5 - 2.5) • S-O • N-H & Si-H • (3.0 - 2.1) > (2.1 - 1.8) • N-H

  20. Match the compounds HF, NaCl, and O2 with the figures above • How do electronegativity values help in determining the polarity of a bond?

  21. Objectives • Learn about ionic and covalent bonds and explain how they are formed • Learn about polar covalent bonds • Understand nature of bonds and their relationships to electronegativity • Understand bond polarity and how it is related to molecular polarity

  22. Bond Polarity & Molecular Polarity • Molecule such as H-F that has a center of positive charge (∂+) and a center of negative charge (∂-) is said to have a dipole moment • Dipole moment represents molecular polarity • Any diatomic molecule with a polar bond has a dipole moment

  23. Some Polyatomic Molecules have dipole moments • Water is a polar molecule (it has a dipole moment) • Properties of H2O • surrounds and attracts both + and - ions • dissolves ionic substances • attract one another strongly (h-bonds) • high boiling temperature

  24. Questions • For each binary molecule given, indicate direction of its dipole moment. Some may have no dipole moment. • H-Cl • H-H • H-I • Br-Br • C-O

  25. Summary • Chemical bond = force holding 2 or more atoms together • Types of Bonds = Ionic and Covalent • Ionic = transfer of e- • Covalent = sharing of e- • Polar Covalent = unequal sharing of e- • Electronegativity = how much an atom “pulls” on e- • Polar bonds -> polar molecules

More Related