A hydrogen atom consists of a proton with an electron whizzing around it. What is in the space between them, and what happens to the space when the atom loses its electron?
Richard Swifte, Darmstadt, Germany
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Thinking of an atom as a nucleus with electrons circling it and empty space in between, like a mini solar system, is a useful analogy, but it isn鈥檛 a true picture. Humans sense material objects in terms of solid particles or waves, so we apply this same imagery to the microworld of atoms. This solar system viewpoint has been replaced by quantum descriptions that produce predictions verified by experiments. These depict a hydrogen atom鈥檚 electron as occupying one of several discrete energy levels, but with a position that is never well defined.
Quantum physics sees the space within the atom not as empty, but as a vacuum fluctuating in energy, represented by the continuous creation and destruction of virtual particle-antiparticle pairs. In a hydrogen atom, the binding of the proton and electron by an electromagnetic field can be viewed as consisting of additional quantum particles 鈥� photons 鈥� occupying the space in between.
In truth, the reality of the atomic world is something we will probably never comprehend fully. Richard Feynman supposedly said: 鈥淚f you think you understand quantum mechanics, you don鈥檛.鈥� To adapt another quote, ascribed to both Arthur Eddington and J. B. S. Haldane, the atomic world isn鈥檛 only stranger than we imagine, it is stranger than we can imagine.
David Muir, Edinburgh, UK
It is more accurate to imagine the electron as a fog where an electron is more likely to be found, rather than a particle. The fog is less dense in some places, like next to the nucleus, and more dense in areas with higher probability of finding an electron.
When an atom loses an electron, the quantum 鈥渨ave function鈥� describing the electron changes so that it has a lower probability of being where it was, but there is a chance that it still could be there.
To answer this question 鈥� or ask a new one 鈥� email lastword@newscientist.com.
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