Eleanor Crabb is a Lecturer in materials chemistry at The Open University and was recently seconded part-time to one of the Centres for Excellence in Teaching and Learning (CETL) awarded to The Open University. Her research interests are in heterogeneous catalysis. She has written on a number of science courses, producing both text based and multimedia materials, including Separation, Purification and Identification, part of the Molecular World Series (a collection of OU undergraduate texts also published by the RSC). Rob Janes is a Staff Tutor at The Open University in Wales. He has co-authored the Elements of the p-block in the Molecular World Series and has produced a CD-ROM-database of chemical demonstrations to accompany the book. Together with Elaine Moore, he was also a co-author of Metal-ligand bonding, another RSC publication. He is a co-presenter of Magic Molecules, a demonstration lecture aimed at schools and the general public. David Johnson is a Visiting Reader in chemistry at The Open University. He was a founding member of the Department and worked on many of the chemistry courses writing a number of copublished texts including Metals and chemical change and Elements of the p Block, part of the Molecular World Series. Elaine Moore is Reader in theoretical chemistry at The Open University. Her research interests lie in the field of computational chemistry. She is the author of OU teaching texts in chemistry, physics and astronomy, including Molecular Modelling and Bonding, in the Molecular World Series, and Metal-ligand bonding. Lesley Smart is a Visiting Senior Lecturer in chemistry at The Open University. She has written on many science courses and chaired the production of the Molecular World Series. She is also an author of two books in the series' The Third Dimension and Separation, Purification and Identification.