solut13c - CHAPTER THIRTEEN BONDING: GENERAL CONCEPTS...

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371 CHAPTER THIRTEEN BONDING: GENERAL CONCEPTS Chemical Bonds and Electronegativity 11. a. Electronegativity: The ability of an atom in a molecule to attract electrons to itself. Electron affinity: The energy change for M(g) + e - M - (g). EA deals with isolated atoms in the gas phase. b. Covalent bond: Sharing of electron pair(s); Polar covalent bond: Unequal sharing of electron pair(s). c. Ionic bond: Electrons are no longer shared, i.e., complete transfer of electron(s) from one atom to another. 12. a. There are two attractions of the form r (-1) (+1) , where r = 1 × 10 -10 m = 0.1 nm. V = 2 × (2.31 × 10 -19 J nm) ú û ù ê ë é nm 0.1 (-1) (+1) = -4.62 × 10 -18 J b. There are 4 attractions of +1 and -1 charges at a distance of 0.1 nm from each other. The two negative charges and the two positive charges repel each other across the diagonal of the square. This is at a distance of 2 × 0.1 nm. V = 4 × (2.31 × 10 -19 ) ú û ù ê ë é 0.1 (-1) (+1) + 2.31 × 10 -19 ú û ù ê ë é (0.1) 2 (+1) (+1) + 2.31 × 10 -19 ú û ù ê ë é (0.1) 2 (-1) (-1) V = -9.24 × 10 -18 J + 1.63 × 10 -18 J + 1.63 × 10 -18 J = -5.98 × 10 -18 J
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372 Note: There is a greater net attraction in arrangement b than in a. 13. Using the periodic table we expect the general trend for electronegativity to be: 1) increase as we go from left to right across a period 2) decrease as we go down a group a. C < N < O b. Se < S < Cl c. Sn < Ge < Si d. Tl < Ge < S e. Rb < K < Na f. Ga < B < O
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CHAPTER 13 BONDING: GENERAL CONCEPTS 373 14. The most polar bond will have the greatest difference in electronegativity between the two atoms. From positions in the periodic table, we would predict: a. Ge-F b. P-Cl c. S-F d. Ti-Cl e. Sn-H f. Tl-Br 15. The general trends in electronegativity used on Exercises 13.13 and 13.14 are only rules of thumb. In this exercise we use experimental values of electronegativities and can begin to see several exceptions. The order of EN using Figure 13.3 is: a. C (2.6) < N (3.0) < O (3.4) same as predicted b. Se (2.6) = S (2.6) < Cl (3.2) different c. Si (1.9) < Ge (2.0) = Sn (2.0) different d. Tl (2.0) = Ge (2.0) < S (2.6) different e. Rb (0.8) = K (0.8) < Na (0.9) different f. Ga (1.8) < B (2.0) < O (3.4) same Most polar bonds using actual EN values: a. Si-F (Ge-F predicted) b. P-Cl (same as predicted) c. S-F (same as predicted) d. Ti-Cl (same as predicted) e. C-H (Sn-H predicted) f. Al-Br (Tl-Br predicted) 16. (IE - EA) (IE - EA)/502 EN (text) 2006/502 = 4.0 F 2006 kJ/mol 4.0 4.0 Cl 1604 3.2 3.2 Br 1463 2.9 3.0 I 1302 2.6 2.7 The values calculated from IE and EA show the same trend (and agree fairly closely) to the values given in the text. Ionic Compounds 17. a. Cu > Cu + > Cu 2+ b. Pt 2+ > Pd 2+ > Ni 2+ c. O 2- > O - > O d. La 3+ > Eu 3+ > Gd 3+ > Yb 3+ e. Te 2- > I - > Cs + > Ba 2+ > La 3+ For answer a, as electrons are removed from an atom, size decreases. Answers b and d follow the radii trend. For answer c, as electrons are added to an atom, size increases. Answer e follows the trend for an isoelectronic series, i.e., the smallest ion has the most protons.
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CHAPTER 13 BONDING: GENERAL CONCEPTS 374 18. a. Mg 2+ :1 s 2 2s 2 2p 6 Sn 2+ : [Kr]5s 2 4d 10 K + s 2 2s 2 2p 6 3s 2 3p 6 Al 3+ s 2 2s 2 2p 6 Tl + :[Xe]6s 2 4f 14 5d 10 As 3+ : [Ar]4s 2 3d 10 b. N 3- , O 2- and F - s 2 2s 2 2p 6 Te 2- : [Kr]5s 2 4d 10 5p 6 c. Be 2+ s 2 Rb + : [Ar]4s 2 3d 10 4p 6 Ba 2+ : [Kr]5s 2 4d 10 5p 6 Se 2- : [Ar]4s 2 3d 10 4p 6 I - : [Kr]5s 2 4d 10 5p 6 19. a. Sc 3+ b. Te 2- c. Ce 4+ and Ti 4+ d. Ba 2+ All of these have the number of electrons of a noble gas.
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This homework help was uploaded on 04/06/2008 for the course CHEM 142 taught by Professor Zoller,williamh during the Fall '07 term at University of Washington.

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solut13c - CHAPTER THIRTEEN BONDING: GENERAL CONCEPTS...

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