CHEM 1000 Lecture Notes - Lecture 18: Pauli Exclusion Principle

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lavendershark790

20 Oct 2016

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Document Summary

S(cid:272)h(cid:396) dinge(cid:396)"s e(cid:395)uation for a multi-electron atom has additional terms for repulsion between electrons. We can consider one electron at a time, in an environment established by nucleus & other electrons. Solving the schr dinger equation for this system gives hydrogen-like orbitals: the same shape, different sizes. At large distances from nucleus this works fine, however at close distances we see effects b/c shielding is not done by only spherical orbitals. Return to radial probability distribution for an electron in an orbital. (the probability multiplied by the surface area at distance r) Example: assume there are 2 electrons in 1s orbital & one electron in either the 2s or 2p orbital. Peak in e- density at around 0 means electron in 2s orbital can penetrate closer to nucleus than 2p. Nuclear attraction at closer distance means 2s e- is held tighter than 2p e- , so the 2s orbital will be at lower energy.

Related Questions

This question is about relationships between the 1s, 2s and 2px orbitals.

(a) Using only the valence atomic orbitals of a hydrogen atom and a fluorine atom, and following the model of Figure 9.46, how many MOs would you expect for the HF molecule? (b) How many of the MOs from part (a) would be occupied by electrons? (c) It turns out that the difference in energies between the valence atomic orbitals of H and F are sufficiently different that we can neglect the interaction of the 1s orbital of hydrogen with the 2s orbital of fluorine. The 1s orbital of hydrogen will mix only with one 2p orbital of fluorine. Draw pictures showing the proper orientation of all three 2p orbitals on F interacting with a 1s orbital on H. Which of the 2p orbitals can actually make a bond with a 1s orbital, assuming that the atoms lie on the z-axis? (d) In the most accepted picture of HF, all the other atomic orbitals on fluorine move over at the same energy into the molecular orbital energy-level diagram for HF. These are called “nonbonding orbitals.” Sketch the energy-level diagram for HF using this information and calculate the bond order. (Nonbonding electrons do not contribute to bond order.) (e) Look at the Lewis structure for HF. Where are the nonbonding electrons?