The understanding of atoms proves to be fundamental to our understanding of physics and chemistry. However, the familiar idea of an atom may not be as straightforward as it seems to be in school textbooks.
The problem with atoms is that they are so hard to study due to their minute size.
An average grain of salt is around 0.3mm, bacteria range around 1-10 micrometres, a virus is around 20-300 nanometres, the width of a strain of DNA is around two nanometres, and then there's the atom at around 0.5-5 Angstroms wide. An angstrom is 10,000,000,000th of a metre.
When you think of an atom, you probably imagine a nucleus at the centre, with electrons orbiting around it. And you're not wrong, but the nucleus of an atom is far smaller than you might think. Secondly, although the electrons do move around the nucleus, it's not as straightforward as picturing a moon orbiting around a planet. There is no way to predict where an electron might be on its orbiting path, as the path changes depending on the number of electrons within an atom.
These electron paths are not spherical as you are taught in school, but rather take on unpredictable shapes and paths.
In more recent years, the idea of an atom has shifted drastically to whole new ideas, such as in String Theory. Here, the existence of a nucleus and electrons are not tiny balls as you might imagine, but rather vibrating strings of energy, each with unique properties. But the issue with string theory is that there are five theories that don't agree with each other.
A particle physicist by the name of Edward Witten studied these five individual predictions within String Theory. He came to a startling conclusion; not one of the five in the field of String Theory was wrong. Rather, they're different ways of looking at the same thing. Due to this discovery, which he dubbed the Matrix Theory, more commonly referred to as M Theory, he would go on to receive the Breakthrough Prize in Fundamental Physics.
Take a look at the video below by the YouTube channel, Jared Owen, on How Small Is An Atom?