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Chapter 4 Suggested solutions for Chapter 4 21 the two extra electrons must go into the degenerate 2pr* MOs 2 2рл* 3 2p 2p INCREASING OF 2 2pr 2po 2so* 2s 2s 2so atomic orbitals of molecular orbitals for atomic orbitals of oxygen atom A molecular oxygen. oxygen atom B The oxygen molecule is linked by one σ bond and two π bonds but there are two unpaired in a π* antibonding MO. These reduce the π bond order to 1 and the unpaired electrons more or less located one on each O atom. These unpaired electrons make oxygen very reactive. Problem 8 Construct MOs for acetylene (ethyne) without hybridization. Purpose of the problem easy to find molecules where you can construct MOs from AOs without hybridization but is one such. You should not be ashamed if you failed to do this problem and you should be proud if you succeeded. We shall not in general construct MOs in this way as it is too but if you simply set up an energy diagram of the AOs, in ascending order as usual, you can satisfactory MOs. ested solution acetylene) has a C-C triple bond. Each carbon bonds to only two other atoms - the other C one of the Hs. Using MO theory, we can see that only the carbon 2s and 2px have the right to bind to two atoms at once which leaves the and 2p₂ to form π MOs with the 2p on the other carbon atom. 2p₂ 2p₂ 1s 2px 1s three σ-MOs 1s 2s 2s 1s 1s 2s 2s 1s combinations of AOs in ethyne that give rise to bonding MOs