Inorganic Chemistry A. Cl and 37 Cl are and

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1 S e l f - s t u d y e x e r c i s e s 1 Inorganic Chemistry A Self-study exercises Chapters 1 and 2 1. Calculate the value of A r for naturally occurring chlorine if the distribution of isotopes is 75.77% Cl and 24.23% Cl. Accurate masses for 35 Cl and 37 Cl are and If A r for Cl is 35.45, what is the ratio of 35 Cl : 37 Cl present in a sample of Cl atoms containing naturally occurring Cl? 3. Calculate the value of A r for naturally occurring Cu if the distribution of isotopes is 69.2% 63 Cu and 30.8% 65 Cu ; accurate masses are and [Ans. 63.5] 4. Why in question 3 is it adequate to write 63 Cu rather than Cu? 5. Calculate A r for naturally occurring Mg if the isotope distribution is 78.99% 24 Mg, 10.00% 25 Mg and 11.01% 26 Mg ; accurate masses are 23.99, and Arsenic is monotopic. What does this statement mean? 7. Given that the principal quantum number, n, is 2, write down the allowed values of l and m l, and determine the number of atomic orbitals possible for n = Using the rules that govern the values of the quantum numbers n and l, write down the possible types of atomic orbital for n = 1, 2 and Write down the possible types of atomic orbital for n = Which atomic orbital has values of n = 4 and l = 2? 11. Give the three quantum numbers that describe a 2s atomic orbital.

2 S e l f - s t u d y e x e r c i s e s Which quantum number distinguishes the 3s and 5s atomic orbitals? 13. Write down two possible sets of quantum numbers that describe an electron in a 2s atomic orbital. What is the physical significance of these unique sets? 14. Write down two possible sets of quantum numbers to describe an electron in a 3s atomic orbital. 15. If an electron has the quantum numbers n = 2, l = 1, m l = 1 and m s = which type of atomic orbital is it occupying? How many radial nodes does each of the following orbitals possess: (a) 2s; (b) 4s; (c) 3p; (d) 5d; (e) 1s; (f ) 4p? 17. Comment on differences between plots of R(r) against r, and 4 r 2 R(r) 2 against r for each of the following atomic orbitals of an H atom: (a) 1s; (b) 4s; (c) 3p. 18. Write down the six sets of quantum numbers that describe the electrons in a degenerate set of 5p atomic orbitals. Which pairs of sets of quantum numbers refer to spin paired electrons? 19. For a neutral atom, X, arrange the following atomic orbitals in an approximate order of their relative energies (not all orbitals are listed): 2s, 3s, 6s, 4p, 3p, 3d, 6p, 1s. 20. Using the concepts of shielding and penetration, explain why a ground state configuration of 1s 2 2s 1 for an Li atom is energetically preferred over 1s 2 2p The bond dissociation enthalpies for the nitrogen nitrogen bond in N 2 and [N 2 ] are 945 and 765 kj mol 1 respectively. Account for this difference in terms of MO theory, and state whether [N 2 ] is expected to be diamagnetic or paramagnetic. 22. Account for the fact that [N 2 ] + is paramagnetic.

3 S e l f - s t u d y e x e r c i s e s Using MO theory, rationalize why the N N bond distance in [N 2 ] + is longer (112 pm) than in N 2 (109 pm). 24. Rationalize why the bond orders in [N 2 ] + and [N 2 ] are both Show that N in NF 3 obeys the octet rule. 26. Show that Se in H 2 Se obeys the octet rule. 27. In which of the following molecules is the octet rule apparently violated by the central atom: (a) H 2 S; (b) HCN; (c) SO 2 ; (d) CO 2 ; (e) SO 3? 28. Within the series of fluorides IF, IF 3 and IF 5, show that the octet rule appears to be obeyed in only one instance for iodine. 29. Predict the structures of (a) XeF 2 and (b) [XeF 5 ]. 30. Predict the structures of, BCl 3, [IF5] 2, [NH 4 ] +, SF 6, XeF 4, AsF 5, [BBr 4 ]. 31. Which of the following species are hydrogen-like: (a) H + ; (b) He + ; (c) He ; (d) Li + ; (e) Li 2+? 32. Draw Lewis structures to describe the bonding in the following molecules: (a) F 2 ; (b) BF 3 ; (c) NH 3 ; (d) H 2 Se; (e) H 2 O 2 ; (f) BeCl 2 ; (g) SiH 4 ; (h) PF Use the Lewis structure model to deduce the type of nitrogen nitrogen bond present in (a) N 2 H 4, (b) N 2 F 4, (c) N 2 F 2 and (d) [N 2 H 5 ] Use VB theory to describe the bonding in the diatomic molecules Li 2, B 2 and C 2. (b) Experimental data show that Li 2 and C 2 are diamagnetic whereas B 2 is paramagnetic. Is the VB model consistent with these facts? 35. Use MO theory to determine the bond order in each of [He 2 ] + and [He 2 ] 2+. (b) Does the MO picture of the bonding in these ions suggest that they are viable species? 36. Construct an MO diagram for the formation of O 2 ; show only the participation of the valence orbitals of the oxygen atoms. (b) Use the diagram to rationalize

4 S e l f - s t u d y e x e r c i s e s 4 the following trend in O O bond distances: O 2, 121 pm; [O 2 ] +, 112 pm; [O 2 ], 134 pm; [O 2 ] 2, 149 pm. (c) Which of these species are paramagnetic? 37. Pick out pairs of isoelectronic species from the following list; not all species have a partner : HF; CO 2 ; SO 2 ; NH 3 ; PF 3 ; SF 4 ; SiF 4 ; SiCl 4 ; [H 3 O] + ; [NO 2 ] + ; [OH] ; [AlCl 4 ]. 38. Use the VSEPR model to predict the structures of (a) H 2 Se, (b) [BH 4 ], (c) NF 3, (d) SbF 5, (e) [H 3 O] +, (f) IF 7, (g) [I3], (h) [I 3 ] +, (i) SO 3, (g) SOF Account for each of the following observations. a. The first ionization energy of K is lower than that of Li. b. BI 3 is trigonal planar while PI 3 is trigonal pyramidal in shape. c. The second ionization energy of He is higher than the first despite the fact that both electrons are removed from the 1s atomic orbital. d. S 2 is paramagnetic. e. In the salt formed from the reaction of Br 2 and SbF 5, the Br Br distance in the Br 2 + ion is 215 pm, i.e. shorter than in Br Use VSEPR theory to account for the structure of NH 3, and suggest an appropriate hybridization scheme for the N atom. 41. Use VSEPR theory to account for the tetrahedral structure of [NH 4 ] Rationalize why H 2 O is bent but XeF 2 is linear. 43. Give a suitable hybridization scheme for the central atom in each of the following: (a) [NH 4 ] + ; (b) H 2 S; (c) BBr 3 ; (d) NF 3 ; (e) [H 3 O] +.

5 S e l f - s t u d y e x e r c i s e s Draw a set of resonance structures (focusing only on those that contribute significantly) for the nitrate ion. (c) Use an appropriate hybridization scheme to describe the bonding in [NO 3 ]. 45. Use an appropriate hybridization scheme to describe the bonding in [BO 3 ] Suggest an appropriate hybridization scheme for each central atom: (a) SiF 4 ; (b) [PdCl 4 ] 2 ; (c) NF 3 ; (d) F 2 O; (e) [CoH 5 ] 4 ; (f ) [FeH 6 ] 4 ; (g) CS 2 ; (h) BF The I I bond distance in I 2 (gas phase) is 267 pm, in the [I 3 ] + ion is 268 pm, and in [I 3 ] is 290pm (for the [AsPh 4 ] + salt). (a) Draw Lewis structures for these species. Do these representations account for the variation in bond distance? (b) Use MO theory to describe the bonding and deduce the I I bond order in each species. Are your results consistent with the structural data?

2011, Robert Ayton. All rights reserved.

2011, Robert Ayton. All rights reserved. Chemical Bonding Outline 1. Lewis Dot Structures 2. Bonds 3. Formal Charges 4. VSEPR (Molecular Geometry and Hybridzation) 5. Common Resonance Structures and Dimerization Review 1. Lewis Dot Structures