top of page

Why Basic Chemistry is the Key to X-ray Physics

The whole reason you’re in x-ray school is to take the ARRT registry and become a registered rad tech. Unfortunately, before you can even get to the registry you have to make it through school-which means passing imaging physics.

Imaging physics is one of the hardest classes in x-ray school and is often treated as a “weed out” class for a reason- it’s complicated and requires applying knowledge and not just memorizing it. To properly apply your knowledge, you first must know the ins and outs of how the basics work.

I want to begin by explaining that- when it comes to x-ray physics, we are really talking about the intersection of chemistry, physics, and biology. It is very difficult to talk only about physics or biology without referencing the other. This is because x-ray physics is APPLIED. On the registry, largely the questions are phrased to determine 1) if you know what principle is being referenced and 2) can you apply that principle to the given scenario and 3) can you correctly determine what that outcome is? To confidently do this, you need to understand the information and how it plays with the other parts.

It can seem daunting- but it doesn’t have to be. Let’s break it down into its most basic parts

Atomic Structure

An atom is the smallest complete building block of matter (anything you can physically touch that has weight). The chair you’re sitting on is made of atoms-you are made of atoms. An atom is often described as looking like a model of the solar system with the sun representing the nucleus and the planets representing electrons in their respective orbital shells.

Particles within an atom:

The center of an atom is called the nucleus and is where you will find protons and neutrons. These two particles cluster together into a dense ball and make up most of the weight of the atom.

Neutrons do not possess a charge and contribute to the atom only in weight and size.

Protons are positively charged and contribute both weight and charge to the atomic nucleus. 

Electrons are negatively charged and cluster around the nucleus, orbiting around at different levels.

It is the difference in charge between the protons and electrons that create a magnetic attraction between the nucleus and the electron cloud. When an atom is placed next to another atom (as is the case with all matter comprised of more than one singular atom) the positive charge of the nucleus of one atom and the nucleus of the next atom repels one another, but the electron cloud of one atom is attracted to the nucleus of the next. It is the interaction of positive and negative charges that creates everything you interact with.


The Electron Cloud

Electrons cluster around the nucleus in a structured cloud made up of orbital levels known as shells. You can think of these shells like the layers of an onion. Each shell contains a specific number of electrons and each of these electrons is attracted with a specific amount of force. This attractive force that ties the electron into its place in the shell is known as “binding energy”

The Nucleus

If most of the interactions we will be worried about happen in the electron cloud- why should we care about the nucleus at all? The nucleus is made of neutrons and protons clustering together (just like the flowers below) and thus is contains almost all the weight of the atom- and this weight is important because it is related to the "blocking power" of an atom. As the atomic number increases the size of the nucleus increases and the better the atoms are at blocking radiation.


Understanding the structure of an atom, what the energy levels are, why the particles stick together in a certain way and how much energy is needed to move them around will be important when we start talking about what x-rays do when they interact with one. Any time you’re struggling with a physics concept at the atomic level- come back to the structure and function of an atom—because most of the time the answer is much easier to find than you think it is.

Studying for the ARRT Registry doesn’t have to be scary! Check out our FREE study strategy here.

If you’re interested in learning more about Radiation Physics and Imaging check out our Personalized Tutoring and Group Classes!



bottom of page