The better way to think about an electron is like a “fog” or a “cloud,” spread throughout the space around an atomic nucleus. When two or more atoms are bound together into a molecule, their electron clouds overlap, and the electron’s extent in space gets even more diffuse. When you press your hand up against another surface, the electromagnetic forces from the electrons on that surface push against the electrons in your hands, causing the electron clouds to distort and deform in their shapes.
This is counterintuitive, of course, because we’re so used to thinking of the fundamental constituents of matter in terms of particles. But it’s better to think of them as quanta instead: behaving like particles under high-energy conditions but behaving like waves under low-energy conditions. When we’re dealing with atoms under normal terrestrial conditions, they’re wave-like, with individual quanta occupying large volumes of space all on their own.
There’s a big problem whenever we rely on our intuition to make sense of the Universe: intuition is borne from experience, and our own personal experience of the Universe is entirely classical. Our Universe is made up of particles at a fundamental phenomena, and collections of particles can compress, rarify, and oscillate in ways that appear wave-like.
But down in the quantum realm of atoms, photons, and individual electrons, wave-like behavior is just as fundamental as particle-like behavior, with only the conditions of the experiment, measurement, or interaction determining what we observe. At very high energies, experiments can reveal that particle-like behavior we’re so familiar with. But under normal circumstances, like the ones we consistently experience in our own bodies, even an individual electron is spread out over an entire atom or molecule.
Inside your body, you aren’t mostly empty space. You’re mostly a series of electron clouds, all bound together by the quantum rules that govern the entire Universe.