Since only one of the Be 2p orbitals has been used in hybridization, there are two unhybridized p orbitals remaining on Be.
The sp hybrid orbitals in gaseous BeCl2. Figure 11.2 atomic orbitals hybrid orbitals orbital box diagrams
The sp hybrid orbitals in gaseous BeCl2(continued). Figure 11.2 orbital box diagrams with orbital contours
The sp2 hybrid orbitals in BF3. Figure 11.3
sp2 and sp3 Hybrid Orbitals
The sp3 hybrid orbitals in CH4. Figure 11.4
Figure 11.5 The sp3 hybrid orbitals in NH3.
Figure 11.5 continued The sp3 hybrid orbitals in H2O.
Figure 11.6 The sp3d hybrid orbitals in PCl5.
The sp3d2hybrid orbitals in SF6. Figure 11.7
Key Points Types of Hybrid Orbitals sp sp2 sp3 sp3d sp3d2 Hybrid Orbitals The number of hybrid orbitals obtained equals the number of atomic orbitals mixed. The type of hybrid orbitals obtained varies with the types of atomic orbitals mixed.
Step 1 Step 2 Step 3 Figure 11.8 The conceptual steps from molecular formula to the hybrid orbitals used in bonding. Molecular shape and e- group arrangement Molecular formula Lewis structure Hybrid orbitals
PROBLEM: Use partial orbital diagrams to describe mixing of the atomic orbitals of the central atom leads to hybrid orbitals in each of the following: PLAN: Use the Lewis structures to ascertain the arrangement of groups and shape of each molecule. Postulate the hybrid orbitals. Use partial orbital box diagrams to indicate the hybrid for the central atoms. SAMPLE PROBLEM 11.1 Postulating Hybrid Orbitals in a Molecule (a) Methanol, CH3OH (b) Sulfur tetrafluoride, SF4 SOLUTION: (a) CH3OH The groups around C are arranged as a tetrahedron. O also has a tetrahedral arrangement with 2 nonbonding e- pairs.
hybridized C atom hybridized O atom single C atom single O atom hybridized S atom S atom SAMPLE PROBLEM 11.1 Postulating Hybrid Orbitals in a Molecule continued (b) SF4 has a seesaw shape with 4 bonding and 1 nonbonding e- pairs.
Some aspects of bonding are not explained by Lewis structures, VSEPR theory and hybridization. (E.g. why does O2 interact with a magnetic field?; Why are some molecules colored?)
For these molecules, we use Molecular Orbital (MO) Theory.
Just as electrons in atoms are found in atomic orbitals, electrons in molecules are found in molecular orbitals.
PROBLEM: Describe the types of bonds and orbitals in acetone, (CH3)2CO. PLAN: Use the Lewis structures to ascertain the arrangement of groups and shape at each central atom. Postulate the hybrid orbitals taking note of the multiple bonds and their orbital overlaps. sp3 hybridized sp3 hybridized sp2 hybridized SAMPLE PROBLEM 11.2 Describing the Bond in Molecules SOLUTION: bond bonds
The Central Themes of MO Theory A molecule is viewed on a quantum mechanical level as a collection of nuclei surrounded by delocalized molecular orbitals. Atomic wave functions are summed to obtain molecular wave functions. If wave functions reinforce each other, a bonding MO is formed (region of high electron density exists between the nuclei). If wave functions cancel each other, an antibonding MO is formed (a node of zero electron density occurs between the nuclei).
Amplitudes of wave functions subtracted. Figure 11.14 An analogy between light waves and atomic wave functions. Amplitudes of wave functions added