Covalent Bonding: Orbitals

Copyright © Houghton Mifflin Company. All rights reserved. 14a–2 The Central Themes of VB Theory Basic Principle A covalent bond forms when the orbitals of two atoms overlap and are occupied by a pair of electrons that have the highest probability of being located between the nuclei. Themes These overlapping orbitals can have up to two electrons that must have opposite spins (Pauli principle). The valence orbitals in a molecule are different from those in isolated atoms.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–3 Figure 12.18: Three representations of the hydrogen 1s

Copyright © Houghton Mifflin Company. All rights reserved. 14a–4 Figure 13.1: (a) The interaction of two hydrogen atoms (b) Energy profile as a function of the distance between the nuclei of the hydrogen atoms.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–5 Figure 13.1: (a) The interaction of two hydrogen atoms (b) Energy profile as a function of the distance between the nuclei of the hydrogen atoms.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–6 Figure 12.19b: Representation of the 2p orbitals.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–7 Hydrogen, H 2 Hydrogen fluoride, HFFluorine, F 2 3 WAYS TO FORM σ MOLECULAR ORBITALS What about The other 2 Atomic p orbitals?

Copyright © Houghton Mifflin Company. All rights reserved. 14a–8 Figure 14.1: (a) Lewis structure of the methane molecule (b) the tetrahedral molecular geometry of the methane molecule.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–9 Figure 14.2: valence orbitals on a free carbon atom

Copyright © Houghton Mifflin Company. All rights reserved. 14a–10 Figure 14.1: (a) Lewis structure of the methane molecule (b) the tetrahedral molecular geometry of the methane molecule.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–11 Figure 14.3: native 2s and three 2p atomic orbitals characteristic of a free carbon atome are combined to form a new set of four sp3 orbitals.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–12 s pxpx pypy pzpz Carbon 1s 2 2s 2 2p 2 Carbon could only make two bonds if no hybridization occurs. However, carbon can make four equivalent bonds. sp 3 hybrid orbitals Energy sp 3 C atom of CH 4 orbital diagram B A B B B Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 321

Copyright © Houghton Mifflin Company. All rights reserved. 14a–13 Figure 14.4: Cross section of an sp3 orbital

Copyright © Houghton Mifflin Company. All rights reserved. 14a–14 The four sp 3 hybrid orbitals in CH 4 Promotion

Copyright © Houghton Mifflin Company. All rights reserved. 14a–15 Figure 11.9 The  bonds in ethane. both C are sp 3 hybridized s-sp 3 overlaps to  bonds sp 3 -sp 3 overlap to form a  bond relatively even distribution of electron density over all  bonds  (Greek sigma) bonds have axial symmetry and good overlap Rotation about C-C bond allowed.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–16 Figure 14.6: Tetrahedral set of four sp 3 orbitals on the carbon atom

Copyright © Houghton Mifflin Company. All rights reserved. 14a–17 Figure 14.7: The nitrogen atom in ammonia is sp 3 hybridized.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–18 The four sp 3 hybrid orbitals in CH 4 Promotion

Copyright © Houghton Mifflin Company. All rights reserved. 14a–19 The four sp 3 hybrid orbitals in CH 4 Promotion

Copyright © Houghton Mifflin Company. All rights reserved. 14a–20 The four sp 3 hybrid orbitals in NH 3 Promotion N

Copyright © Houghton Mifflin Company. All rights reserved. 14a–21 The four sp 3 hybrid orbitals in NH 3 Promotion N

Copyright © Houghton Mifflin Company. All rights reserved. 14a–22 Figure 11.5 The sp 3 hybrid orbitals in H 2 O Lone pairs

Copyright © Houghton Mifflin Company. All rights reserved. 14a–23 Diamond - sp 3 hybridized C

Copyright © Houghton Mifflin Company. All rights reserved. 14a–24 Figure 14.8: The hybridization of the s, p x, and p y atomic orbitals results in the formation of three sp 2 orbitals centered in the xy plane. NB: The remaining p orbital can be empty or serve another function

Copyright © Houghton Mifflin Company. All rights reserved. 14a–25 The three sp 2 hybrid orbitals in BF 3 Promotion Region of overlap Note the single left over Unhybridized p orbital on B

Copyright © Houghton Mifflin Company. All rights reserved. 14a–26 Hybrid Orbitals 2s2s2p2p Ground-state B atom s pxpx pypy pzpz Energy sp 2 2p2p B atom of BH 3 orbital diagram hybridize s orbital 2s2s2p2p B atom with one electron “promoted” sp 2 hybrid orbitals p orbitals sp 2 hybrid orbitals shown together (large lobes only) three sp s hybrid orbitals H H H B

Copyright © Houghton Mifflin Company. All rights reserved. 14a–27 Figure 14.10: When one s and two p oribitals are mixed to form a set of three sp 2 orbitals, one p orbital remains unchanged and is perpendicular to the plane of the hybrid orbitals.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–28 Figure 14.13: (a) The orbitals used to form the bonds in ethylene. (b) The Lewis structure for ethylene.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–29 The plastics shown here were manufactured with ethylene. Source: Comstock - Mountainside, NJ

Copyright © Houghton Mifflin Company. All rights reserved. 14a–30 Figure 14.11: The σ bonds in ethylene.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–31 Figure 14.12: A carbon-carbon double bond consists of a σ bond and a π bond.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–32 Figure 14.48: The benzene molecule consists of a ring of six carbon atoms with one hydrogen atom bound to each carbon; all atoms are in the same plane. Sp2 hybridized

FIGURE 14.49: Sigma Bonding System in Benzene

FIGURE 14.50: (a) Pi MO System in Benzene, (b) Delocalized Pi MO Over Entire Ring of C Atoms

Copyright © Houghton Mifflin Company. All rights reserved. 14a–35

FIGURE 14.51: (a) Pi Bonding System in NO 3 -, (b) Delocalized Electrons in the pi MO System of NO 3 - Ion

Copyright © Houghton Mifflin Company. All rights reserved. 14a–37 Graphite – sp 2 hybridized C

Copyright © Houghton Mifflin Company. All rights reserved. 14a–38 Fullerene-C 60 and Fullerene-C 70 What hybridization of C describes the structures?

Copyright © Houghton Mifflin Company. All rights reserved. 14a–39 Figure 14.14: When one s orbital and one p orbital are hybridized, a set of two sp orbitals oriented at 180 degrees results.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–40 The sp hybrid orbitals in gaseous BeCl 2 Why are sp hybrids invoked? Because if Be made one bond with its 2s and one bond with a 2p orbital, then the two Be-Cl bonds would have different strengths & lengths. But both bonds are identical. Promotion Promote to create two half filled orbitals that participate in bond formation Filled 2s orbital can’t bond to Cl

Copyright © Houghton Mifflin Company. All rights reserved. 14a–41 The two sp hybrid orbitals in gaseous BeCl 2 Note the two “leftover” p orbitals of Be Region of overlap

Copyright © Houghton Mifflin Company. All rights reserved. 14a–42 Figure 14.15: The hybrid orbitals in the CO 2 molecule

Copyright © Houghton Mifflin Company. All rights reserved. 14a–43 Figure 14.16: orbital energy level diagram for the formation of sp hybrid orbitals of carbon.

Copyright © Houghton Mifflin Company. All rights reserved. 14a–44 Figure 14.17: Orbitals of an sp hybridized carbon atom

Copyright © Houghton Mifflin Company. All rights reserved. 14a–45 sp 2 hybridization of an oxygen atom 1 trigonal Bond with 2 lone pairs + 1 for a pi bond sp 2 pxpx 4 hybridized orbitals sp 2 pxpx

Copyright © Houghton Mifflin Company. All rights reserved. 14a–46 Figure 14.18: Orbital arrangement for an sp 2 hybridized oxygen atom

Copyright © Houghton Mifflin Company. All rights reserved. 14a–47 Figure 14.19: (a) Orbitals predicted by the LE model to describe (b) The Lewis structure for carbon dioxide

Copyright © Houghton Mifflin Company. All rights reserved. 14a–48 Hybrid Orbitals spsp 2 sp 3 sp 3 dsp 3 d 2 Types of Hybrid Orbitals Shapes: linear triangular tetrahedral trig. bipyram. Octahedral # orbitals:

Copyright © Houghton Mifflin Company. All rights reserved. 14a–49 The four sp 3 hybrid orbitals in NH 3 Promotion N

Copyright © Houghton Mifflin Company. All rights reserved. 14a–50 The four sp 3 hybrid orbitals in NH 3 Promotion

Copyright © Houghton Mifflin Company. All rights reserved. 14a–51 Figure 14.20: (a) An sp hybridized nitrogen atom (b) The s bond in the N 2 molecule (c) the two p bonds in N 2 are formed

Copyright © Houghton Mifflin Company. All rights reserved. 14a–52 The conceptual steps from molecular formula to the hybrid orbitals used in bonding. Molecular formula Lewis structure Molecular shape and e - group arrangement Hybrid orbitals Step 1Step 2Step 3

Copyright © Houghton Mifflin Company. All rights reserved. 14a–53 sp 3 hybridization of a carbon atom

Copyright © Houghton Mifflin Company. All rights reserved. 14a–54 sp 3 hybridization of a carbon atom

Copyright © Houghton Mifflin Company. All rights reserved. 14a–55 sp 3 hybridization of a nitrogen atom 3 tetrahedral bonds with 1 lone pair sp 3

Copyright © Houghton Mifflin Company. All rights reserved. 14a–56 sp 3 hybridization of a nitrogen atom N

Copyright © Houghton Mifflin Company. All rights reserved. 14a–57 sp 3 hybridization of a oxygen atom 2 tetrahedral bonds with 2 lone pairs sp 3

Copyright © Houghton Mifflin Company. All rights reserved. 14a–58 sp 3 hybridization of a oxygen atom

Copyright © Houghton Mifflin Company. All rights reserved. 14a–59 sp 2 hybridization of a carbon atom 3 trigonal Bonds + 1 for a pi bond sp 2 pxpx 4 hybridized orbitals sp 2 pxpx

Copyright © Houghton Mifflin Company. All rights reserved. 14a–60

Copyright © Houghton Mifflin Company. All rights reserved. 14a–61

Copyright © Houghton Mifflin Company. All rights reserved. 14a–62

Copyright © Houghton Mifflin Company. All rights reserved. 14a–63

Copyright © Houghton Mifflin Company. All rights reserved. 14a–64 sp 2 hybridization of an oxygen atom 1 trigonal Bond with 2 lone pairs + 1 for a pi bond sp 2 pxpx 4 hybridized orbitals sp 2 pxpx

Copyright © Houghton Mifflin Company. All rights reserved. 14a–65 Figure 14.19: (a) Orbitals predicted by the LE model to describe (b) The Lewis structure for carbon dioxide

Copyright © Houghton Mifflin Company. All rights reserved. 14a–66 sp hybridization of a carbon atom 4 hybridized orbitals sp 2 linear bonds + 2 for pi bonds sp pypy pypy pxpx pxpx

Copyright © Houghton Mifflin Company. All rights reserved. 14a–67

Copyright © Houghton Mifflin Company. All rights reserved. 14a–68 sp hybridization of an nitrogen atom 4 hybridized orbitals sp 1 linear Bonds with 1 lone pair + 2 for pi bonds sp pypy pypy pxpx pxpx

Copyright © Houghton Mifflin Company. All rights reserved. 14a–69 Figure 14.20: (a) An sp hybridized nitrogen atom (b) The s bond in the N 2 molecule (c) the two p bonds in N 2 are formed

Copyright © Houghton Mifflin Company. All rights reserved. 14a–70 Figure 14.21: A set of dsp 3 hybrid orbitals on a phosphorous atom

Copyright © Houghton Mifflin Company. All rights reserved. 14a–71 Hybridization Involving d Orbitals 3s 3p 3d promote five sp 3 d orbitals 3d3d F F F P F F A BeBe BeBe BeBe BaBa BaBa Trigonal bipyramidal hybridize degenerate orbitals (all EQUAL) unhybridized P atom P = [Ne]3s 2 3p 3 vacant d orbitals

Copyright © Houghton Mifflin Company. All rights reserved. 14a–72 Figure 11.6 The five sp 3 d hybrid orbitals in PCl 5

Copyright © Houghton Mifflin Company. All rights reserved. 14a–73 Figure 14.22: The orbitals used to form the bonds in the PCL 5 molecule

Copyright © Houghton Mifflin Company. All rights reserved. 14a–74 Figure 14.23: An octahedral set of d 2 sp 3 orbitals on a sulfur atom

Copyright © Houghton Mifflin Company. All rights reserved. 14a–75 Figure 11.7 The six sp 3 d 2 hybrid orbitals in SF 6

Copyright © Houghton Mifflin Company. All rights reserved. 14a–76 Figure 14.24: The relationship among the number of effective pairs, their spatial arrangement, and the hybrid orbital set required

Copyright © Houghton Mifflin Company. All rights reserved. 14a–77 Figure 14.24: The relationship among the number of effective pairs, their spatial arrangement, and the hybrid orbital set required (cont’d)

Copyright © Houghton Mifflin Company. All rights reserved. 14a–78 Figure 11.8 The conceptual steps from molecular formula to the hybrid orbitals used in bonding. Molecular formula Lewis structure Molecular shape and e - group arrangement Hybrid orbitals Figure 10.1 Step 1 Figure Step 2Step 3 Table 11.1