Page 102 - Science at the nanoscale

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RPS: PSP0007 - Science-at-Nanoscale
June 12, 2009
From Atoms and Molecules to Nanoscale Materials
92
into the ring-shaped head group can be reversibly controlled
using radiation at different wavelengths.
Further Reading
M. Ladd, Chemical Bonding in Solids and Fluids (Ellis Horwood,
1994).
P. A. Cox, The Electronic Structure and Chemistry of Solids (Oxford
University Press, 1991).
L. Smart and E. Moore, Solid State Chemistry — An Introduction
(Chapman & Hall, 1992).
V. Balzani, A. Credi, F. M. Raymo and J. F. Stoddart, Artificial
Molecular Machines, Angew. Chem. Int. Ed. 39, 3348–3391 (2000).
Exercises
4.1 On the basis of their electronic structures, answer the
following questions for the first row of elements in the
Periodic Table: (i) Li forms Li ions readily in solids and
+
solutions, why does Be not form Be
ions in solids?
2+
(ii) Why is there a discontinuity for the trend of varia-
tion for ionization energy from N to O? (iii) How do the
electron negativities vary from Li to F atom and why?
(iv) Which of the elements in (iii) have tendency to form
anions?
4.2 The bond distance of HCl molecule is 1.27 angstrom.
Determine what portion of a unit electron charge is trans-
ferred from hydrogen atom to chlorine atom.
4.3 In addition to hydrogen bonding, there are at least two
other interactions that are important for DNA double ch04
helix (Fig. 4.14). Identify these and give a brief descrip-
tion of each.
4.4 The coordination number of an ion A in ionic solid AB is
determined by the ratio of their radius r A /r B . Work out
the maximum coordination number possible for A if the
ratio is 0.3.
4.5 Cis-trans isomerisation such as that shown in Figure 4.30
requires energy input. Convert these energies into the
usual unit of kJ mol −1 .