Why don't electrons crash into atoms?

23 June 2020

QUANTUM-PHYSICS

Abstract art of an atom

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Question

If electrons are negative, and the centre of an atom is positive, and opposites attract, why don't electrons crash into atoms?

Answer

We put this quantum conundrum to University of Cambridge chemist Ljiljana Fruk...

Ljiljana - Yeah. So, I mean, it's an extremely interesting question, of course, because you know, this is how we would imagine if we imagine an electron as a negatively charged particle, hitting the positively charged nucleus. But we can't look at the electron as the conventional classical particle. It's a tiny particle and it can't be treated as a classical particle that has a defined position and velocity. But rather as a diffused cloud, let's say, which is defined by quantum physics. And now, without going into quantum physics, we could also say that an electron behaves like a wave. And as it gets, for example, closer to the nucleus, it gets confined in the smaller volume. And for that, we need to apply now a certainty principle that if you know a position of the electron, if it gets confined into the certain volume, we don't know really a momentum or the, or the speed of this electron, but basically what happens as the election gets closer to the nucleus, the wavelength of this electron gets shorter. The shorter wavelength means it has lots of energy and there is a certain point of an electron being around the nucleus where this energy is going to be enough to overcome the attractive force from the nucleus. So basically the energy, the huge energy of electrons, will balance the attractive force of the nucleus. And so the electron is going to be diffused as a cloud around the nucleus, but it's never going to fall into it. So basically we need to stop treating or thinking about the electron as a classical particle, which is moving in the circles around the nucleus. But we need to think that there are some quantum physics rules that apply to it.

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