CHM333H5 Lecture Notes - Lecture 2: Atomic Number

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9 Nov 2016

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Spherical: equal energy orbitals when ligands come in equally. Non-spherical: assume that incoming ligands are point charges, orbitals pointing towards ligands become higher in energy and ligands pointing away from ligand are lower in energy. Square planar: assume that ligands pulled away from metal along z axis, systems with 8d electrons such as pt and pd. Tetrahedral: ligands not aligned with any orbital: assume t ~ 1/2 0. Low spin = 4 x 2/5 0 = 8/5 0. High spin = 3 x 2/5 0 - 1 x 3/5 0 = 3/5 0. Tetrahedral = 2 x 3/5 t - 2 x 2/5 t = 2/5 t ~ 1/5 0. *** octahedral more stable than tetrahedral, except d5 and d10 because making 6 bonds (exothermic) is more stable than 4 bonds. 1-3 go into t2g orbitals closer to the nucleus while 4-5 go into eg orbitals which are further from the nucleus.

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Shown below is a qualitative diagram of the atomic orbital energies for an Na atom. The number of orbitals in each subshell is not shown.

(a) Are all of the subshells for n = 1, n = 2, and n = 3 shown? If not, what is missing?

(b) The 2s and 2p energy levels are shown as different. Which of the following is the best explanation for why this is the case? (i) The 2s and 2p energy levels have different energies in the hydrogen atom, so of course they will have different energies in the sodium atom, (ii) The
energy of the 2p orbital is higher than that of the 2s in all many-electron atoms. (iii) The 2s level in Na has electrons in it, whereas the 2p does not.
(c) Which of the energy levels holds the highest-energy electron in a sodium atom?
(d) A sodium vapor lamp (Figure 7.23) operates by using electricity to excite the highest-energy electron to the next highest-energy level. Light is produced when the excited electron drops back to the lower level. Which two energy levels are involved in this process for the Na atom?

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Benzene is an organic chemical compound with the molecular formula C6H6. In the benzene molecule, carbon atoms form a ring with alternating single and double bonds connecting them. Thus, each individual carbon atom forms one ? bond with another carbon atom and one ? and one ? bond with another carbon atom. Each carbon atom also forms one ? bond with a hydrogen atom. Identify which types of orbitals overlap to form the bonds between the atoms in a benzene molecule. Drag the appropriate labels to their respective targets.

Attached is picture. Please explain/show work, will give 5 stars to correct answer, thank you very much! :)

Chemical bonds are formed by linear combinations of atomic orbital's. These atomic orbital's should have compatible energies. An axial overlap of these orbitals results in the formation of a sigma bond, whereas a lateral overlap results in the formation of a pi bond. When two atomic orbitai's on different atoms approach each other, two molecular orbital's are formed: one bonding molecular orbital and one antibonding molecular orbital. The bonding molecular orbital has a lower energy than the corresponding atomic orbital's: antibonding orbital's have higher energies than the corresponding atomic orbital's. An example using the hydrogen molecule is shown here. However, the same rule applies to systems with multiple atomic orbital's. For each atomic orbital that overlaps, one molecular orbital must form. In the diagram below. 1s orbitais from two hydrogen atoms combine to form one bonding sigma1 orbital and one antibonding orbital. The total number of bonding and antibonding orbital's is always equal to the number of orbital's that overlap. Similarly, molecular orbital's can also be formed by the overlapping of hybrid orbital's. The hybrid orbital's are formed by the linear combination of different atomic orbital's of nearly equal energy on the same atom. The atomic orbital's of nearly equal energy undergo a process of mixing and reorientation to form new orbital's of lower energy. This process is called hybridization For example, hybridization of one s and two p orbital's on an atom forms three sp2 hybrid orbital's. Benzene is an organic chemical compound with the molecular formula C6H6. In the benzene molecule, carbon atoms form a ring with alternating single and double bonds connecting them. Thus, each individual carbon atom forms one sigma bond with another carbon atom and one sigma and one pi bond with another carbon atom. Each carbon atom also forms one sigma bond with a hydrogen atom. Identify which types of orbital's overlap to form the bonds between the atoms in a benzene molecule.

CHM333H5 Lecture Notes - Lecture 2: Atomic Number

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