Snip, snip those model molecules

Medical Origami
February 9, 1996

I think I have found my level: at last, I am sent for review a cut-out book of paper models. Gone, maybe, are the days when I was expected to deal with words. There are words, a few anyway, but the bulk of this book is an invitation to hack at the pages, to cut out the shapes, and to build them into elegant realisations of molecules and even of extended solids.

The scale is 1:300 000, which if adopted by the Ordnance Survey would have England stretched across the diameter of the Earth's orbit and every pebble mapped across three kilometres of paper. But this enormous magnification is needed to be able readily to handle, and perceive, the ultimately small, with a molecule of ammonia about an inch across.

Of course, it is not classical origami, for to make these models one needs to adopt the barbarian device of cutting as well as folding. Nevertheless, it is pleasing to fold paper into phosphate instead of crane, and to build an object of education as well as charm.

The models are all drawn to scale, and the fact that many at first sight seem repetitive is in fact an aspect of their pedagogical value. There are subtle nuances of shape, of bond angle, bond length, and overall size that are brought quite clearly home by building trigonal pyramid after trigonal pyramid and tetrahedron after tetrahedron.

The author, too, is sensitive to the issues that these nuances raise, and raises questions about the features which instructors might ask their students to discuss. A helpful feature is a reasonably lengthy and detailed answer section to these questions, with some thought-provoking answers. Another function of the text (one that suggests that it is better to photocopy the pages rather than to cut up the originals) is as a database of angles, lengths, shapes, and sizes arranged suggestively and attractively on the page. I shall certainly use it that way.

Paper models of molecules might seem old hat with all the glitz of molecular modelling packages for computers, with shaded balls nestling into one another, glinting in simulated light and giving an illusion of the tangible. Molecular graphics are now an ineluctable tool of modern chemistry, and have helped to open the eyes of all chemists to aspects and properties that were otherwise hard to understand and even to visualise without help. Yes, this is old hat, but it is not the function of this handy paper production to displace what can be learned from dazzling graphics. These models give a sense of immediacy and a sense of familiarity of trends, which also help to generate that utmost quality of a chemist: insight into the molecular world and the personalities of the invisible. Besides, you could always colour these models fancifully, and hang them up as Christmas decorations.

Who will use this book? Any chemist who is young at heart might like to snip, fold, and glue, and in doing so might well come away with a deeper knowledge of the bricks of their trade. Any teacher should be able to use them as an aid to teaching, at all levels. Parents who want to bring molecules into the orbit of their children at an early stage, might well find plenty of resources here. Anything that renders chemistry less abstract, more tangible, is to be welcomed, and this unassuming, engaging publication deserves to be well received.

P. W. Atkins is a lecturer in physical chemistry, University of Oxford.

Medical Origami: Precision Scale Models from Paper

Author - Robert M. Hanson
ISBN - 0 935702 30 X
Publisher - University Science Books
Price - £21.95
Pages - 223

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