1 / 18

Covalent Bonding

Covalent Bonding. Sec. 8.4: Molecular shape. Objectives. Discuss the VSEPR bonding theory Predict the shape of and the bond angles in a molecule Define hybridization. VSEPR Model. Molecular shape determines many physical and chemical properties of compounds

henriettal
Télécharger la présentation

Covalent 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. Covalent Bonding Sec. 8.4: Molecular shape

  2. Objectives • Discuss the VSEPR bonding theory • Predict the shape of and the bond angles in a molecule • Define hybridization

  3. VSEPR Model • Molecular shape determines many physical and chemical properties of compounds • The ValenceShell Electron Pair Repulsion model is used to determine molecular geometry (shape).

  4. VSEPR Model • Molecular shape is determined by the overlap of orbitals that are sharing electrons • Atoms/orbitals assume a shape that minimizes the repulsion of shared and unshared pairs of electrons around the central atom.

  5. VSEPR Model • Shared pairs (covalent bonds) repel one another • Lone pairs also repel one another • In addition, lone pairs repel shared pairs and push shared pairs closer to each other (because of the relatively large orbitals of the lone pairs) • Consider an analogy ...

  6. VSEPR Model • Repulsions of electron pairs for each other results in atoms being at fixed angles to each other. • The angle formed by 2 terminal atoms and the central atom is a bond angle. • Table 6 (pg. 263) summarizes molecular shapes and angles predicted by the VSEPR theory.

  7. Molecular shape: Linear • No lone pairs present on central atom. • 2 bonding pairs present • Maximum separation is attained at a bond angle of 1800 Ex. BeCl2

  8. Molecular shape: Linear • The shape for a central atom with double or triple bonds is linear. These types of bonds are rigid and hold the atoms involved in a linear configuration.

  9. Trigonal Planar • No lone pairs present on central atom. • 3 bonding pairs present. • Maximum separation is attained at bond angles of 1200 Ex. AlCl3

  10. Tetrahedral • No lone pairs present on central atom. • 4 bonding pairs present. • Maximum separation is attained at bond angles of 109.50 Ex. CH4

  11. Trigonal Pyramidal • 1 lone pair present on central atom • 3 bonding pairs present • Lone pair takes up more space than a bonding pair • Bonding pairs are pushed closer together • Bond angles are 107.30

  12. Bent • 2 lone pairs present • 2 bonding pairs present • Lone pairs take up more space than bonding pairs • Bond angles are 104.50

  13. Trigonal Bipyramidal • No lone pairs present • 5 bonding pairs present • Bond angles are 900 vertical to horizontal • Bond angles are 1200 horizontal to horizontal

  14. Octahedral • No Lone pairs present • 6 bonding pairs present • Bond angles are 900

  15. Hybridization • When 2 of the same type of object combine, a hybrid results that has characteristics of both objects. • During bonding, orbitals undergo hybridization. • Hybridization is a process in which atomic orbitals are mixed to form new, identical hybrid orbitals.

  16. CH4 (methane) • Carbon has 4 valence electrons: [He] 2s2 2p2 • The electrons in the s orbital unpair: [He] 2s1 2p3 • Hybrid orbitals - formed in bonding from the 1 “s” and 3 “p” orbitals - are called sp3

  17. Hybridization • Like the carbon in methane, hybridization of orbitals occurs in all covalent compounds. • Depending on exactly which orbitals hybridize, the “name” of the hybridization can vary. Recall it is called “sp3” for methane. • The 5th column of the table on pg. 263 gives the names of the hybridizations associated with each shape.

  18. Practice Problems • Determine the shape, bond angles, and hybridization of • PH3 • BF3 • NH4+ • OCl2 • KrF2

More Related