What's the distance from a nucleus to an electron? © Getty Images

What’s the distance from a nucleus to an electron?

The Bohr radius, is the estimated distance between protons in the nucleus and electrons - but electrons aren't solid, stationary particles...

Asked by: Alan Dunne, Ireland

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The simple answer would be about one-twentieth of a nanometre. But this would only be reasonable if the electron were a solid particle.

Quantum mechanics tells us that we can only speak of an electron’s orbital position in a statistical sense. We talk about the electron’s ‘wave function’, which gives us a measure of that probability, which has a value arbitrarily close to the nucleus, and also on the other side of the galaxy. The maths work, even though we can’t picture what it is working on.

Are atoms expanding as the Universe expands? © Getty Images

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