Are atoms expanding as the Universe expands? © Getty Images

In an atom, what fills the space between particles?

Asked by: Harvey Smith

At school, we’re taught to picture atoms as a kind of mini solar system, with electrons as tiny ‘planets’ whizzing around the nucleus. So it’s natural to think that most of the atom is nothing but empty space.


However, quantum theory has revealed a far stranger reality. Rather than solid objects orbiting the nucleus, the electrons are more like fuzzy clouds whose density varies from place to place. This cloud-like nature of electrons means that there’s a probability of them being anywhere in the atom, making it meaningless to talk of empty space lying between them and the nucleus.

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