Peter Atkins (Oxford) is legendary among chemists for his prolific writings (almost 60 books and still writing) and his gift for presenting difficult material in new, accessible, and highly readable ways. Reading his descriptions of an elementary topic can make me feel like I am understanding it for the first time. In his latest book, What is Chemistry? (Oxford, $19.95, ISBN 978-0-19-968398-7), he tackles the arrangement of electron “clouds” inside the atom in this way:
“I need to make more precise the nature and structure of those clouds, for they are not just regions of swirling mist … Electrons surround the nucleus in layers, rather like real clouds lying above each other, but encircling the entire atom. The concept of an electron being a ‘cloud’ needs a quick word of explanation. The cloud is really a cloud of probability: where it is dense, the electron is likely to be found; where it is sparse, the electron is unlikely to be found.”
He also deals with a common misunderstanding:
“It is often said that atoms are mostly empty space. That simply isn’t true. The cloudlike distributions of electrons fill the whole of space around the tiny fly-in-a-stadium-sized nucleus. Admittedly the cloud is very thin in parts; but it is there and all-pervasive.”
I guess you could say that an atom is filled with ‘probability’.
