By the early twentieth century it was known that atoms were made of parts – Thomson’s discovery of the electron had established that – but it wasn’t known how many parts there were or how they fitted together or what shape they took. Some physicists thought that atoms might be cube-shaped21, because cubes can be packed together so neatly without any wasted space. The more general view, however, was that an atom was more like a currant bun or a plum pudding: a dense, solid object that carried a positive charge but that was studded with negatively charged electrons, like the currants in a
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Earlier thoughts about the shape and structure of Atom
