Fall 2015 Exam III 1. c 9. b 16. (next slides) 2. b 10. a 17. (next slides) 3. d 11. d 4. b 12. e 5. a 13. d 6. c 14. c 7. a 15. e 8. e  

16. a) 16. a(i) (ii) FALSE – CCl4 is an example. There is a bond dipole between each C–Cl bond, however as a whole, there is symmetrical electron distribution (and the dipole moments cancel, causing no net dipole moment). (iii) TRUE – Examples will vary, however verify that the series listed has the same number of electrons and thus the same electron configuration. (iv) FALSE – The ranking should be Ne < N2 < CO < BeO.

16. b) 16. b(i) The correct statement is III. (ii) Element M may have a larger or smaller atomic radius than element Z, depending on how many electrons (and thus energy levels) are in each element. For example, if element M contains electrons that are in higher energy levels than element Z, than M will have a larger atomic radius because the electrons are further from the nucleus. Rb versus F is an example of this. Rb has 37 protons and outer electrons in the 5th energy level whereas F has 9 protons and outer electrons only in the second energy level, making Rb larger than F. However, if element M and Z have outer electrons both in the same energy level, than M with more protons will have a smaller radius than Z due to a higher nuclear charge (more pull from nucleus). F versus Be is an example where F has 9 protons but is smaller than Be with 4 protons.

17. 17. a) b) Geometry – trigonal bipyramid; Shape – see saw; This molecule is POLAR. c) Geometry refers to how the atoms and lone pairs arrange themselves around the central atom to maximize the distance and minimize electron repulsions. Shape describes what the molecule looks like by looking at the attached atoms and ignoring the lone pairs. These are used to look for symmetrical electron distribution around the central atom. Generally, if the electron distribution is symmetrical, which we can tell from the molecule’s shape and connecting atoms, the molecule is nonpolar. If the electron distribution is not symmetrical, then the molecule is polar (and has a net dipole moment). d) London dispersion – all molecules have these; due to random-induced dipoles. Dipole-dipole – due to charge separation of polar molecule