1 / 10

CHAPTER 9

CHAPTER 9. AP/HONORS CHEMISTRY. MOLECULAR GEOMETRY. VSEPR - valence-shell electron pair repulsion IDEAL GEOMETRIES Type geometry bond angle AB 2 (2 e- pairs) Linear 180 o example on board

rocco
Download Presentation

CHAPTER 9

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. CHAPTER 9 AP/HONORS CHEMISTRY

  2. MOLECULAR GEOMETRY • VSEPR - valence-shell electron pair repulsion • IDEAL GEOMETRIES • Type geometry bond angle • AB2 (2 e- pairs) Linear 180o example on board • AB3 (3 e- pairs) Triangular 120o example on board Planar • AB4 (4 e- pairs) Tetrahedral 109.5o example on board • AB5(5 e- pairs) Trigonal 120o & 180o example on board bipyramidal • AB6(6 e- pairs) Octahedral 90o example on board

  3. EFFECT OF UNPAIRED ELECTRONS • Type geometry bond angle • AB2E (2 e- pairs, Bent example on board 1 lone pair) • AB2E2 (2 e- pairs, Bent 105o example on board 2 lone pairs) • AB3E (3 e- pairs, Triangular 107o example on board 1 lone pair) pyramidal • the electron pair geometry approximately the same as that observed when only single bonds exist

  4. CONTINUED • the molecular geometry is quite different with lone pairs. Why? • lone pairs take up more space than when bonded • consider NH3 it has a electronic pair geometry of tetrahedral but the angle is 107o • the water molecule is nonlinear because of lone pairs 105o

  5. OTHER LONE PAIR GEOMETRIES • AB4E see-saw SF4 • AB3E2 T-shaped ClF3 • AB2E2 linear XeF2 • AB5E square pyramidal BrF5 • AB4E2 square planar XeF4 • when dealing with geometries multiple bonds behave like single bonds

  6. CONTINUED • the geometry depends upon how many terminal atoms the central atom has around it and the number of unshared electrons • the VSEPR model can be extended to molecules which do not have a single central atom. C2H2 and C2H4

  7. POLARITY OF MOLECULES • Polar • large (not large enough to form ionic bonds) electronegative difference • unequal share of the electrons • nonpolar equal sharing • the degree of polarity is measured by its dipole moment • π = Qr, Q = charge at either end, r = distance • 1 debye = 3.33 x 10-30 coulomb-meters H-Cl 1.03D bond length 1.36 Ǻ

  8. CONTINUED • is it easy to determine whether a diatomic molecule is polar. Why? • check if the elements are the same or different • if a molecule contains more than two atoms, we must decide whether the whole molecule is polar or nonpolar • the are two criteria for determining the polarity of a molecule: bond polarity and molecular geometry

  9. ATOMIC ORBITALS • Sigma bonds σ • single lobe where the electron density is concentrated in the region directly between two bonded atoms • pi bond π • this orbital has two lobes one above the bond axis and one below. The electron density is zero • all single bonds are sigma bonds and any other bond in a double or triple bond will be pi bonds • on board • hybrid orbitals on board

  10. DELOCALIZE BONDING • The bonds are given to all atoms i.e. benzene on board makes it stable (aromaticity) • magnetism - molecules with one or more paired electrons are attracted to a magnetic field • the more unpaired electrons, stronger attraction- paramagnetism • with no unpaired electrons, weak repulsion - dimagnetism

More Related