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REVIEW OF THE ATOM

After completing this section you will be able to do the following:

  • Discuss the origin of magnetism.
  • Discuss why some materials can be magnetized while others cannot.

The study of atoms, electrons, neutrons, and protons is so complex that throughout history scientists have developed several models of the atom. From the early Greek concept of the atom, about 2400 years ago, to today's modern atomic model, scientists have built on and modified existing models, as new information was discovered. There are still concepts on which scientists do not fully agree. In an attempt to simplify the concept and describe how some materials become magnetized, we are using a simplification of the Niels Bohr Model of the atom. Niels Bohr was a Danish scientist and made his model in 1913. In his model Bohr depicted electrons spinning and orbiting the nucleus of an atom. In our exercise, the electron appears to orbit in the same path around the nucleus, but electrons do not really orbit in the same path.  They change their path with each revolution and are commonly described as existing in clouds that surround the nucleus of an atom. Because electrons move so quickly, it is impossible to see where they are at a specific moment in time.

As the electrons circle the nucleus of the atom, they also spin, similar to the way the Earth spins on its axis.

Questions

  1. What are the two types of motion that the electrons of an atom exhibit?
  2. What scientist's model of the atom do we generally use?

What is the origin of magnetism?

The origin of magnetism is a very complicated concept. In fact, there are some details about magnetism on the atomic scale that scientists still do not fully agree on. To begin to understand where magnetism originates and why some materials can be magnetized while others cannot, requires a fair amount of quantum theory. Quantum theory is the study of the jumps from one energy level to another as it relates to the structure and behavior of atoms. However, explaining quantum theory is well beyond the scope of this material, so this subject will be reserved for high school and college chemistry and physics classes. Nevertheless, the basic scientific principles of magnetism can be explained if a few generalizations and simplifications are made.

What does matter consist of?

First, you must recall that all matter is made up of atoms. Atoms have a positively charged center called the nucleus. A nucleus contains one or more protons and neutrons and is orbited by one or more negatively charged particles called electrons. A simplified animation of an atom is what you observed above. You should have concluded that the electrons spin as they travel around the nucleus (which contain protons and neutrons) much like the earth spins as it orbits the sun. As the electrons spin and orbit the nucleus, they produce a magnetic field. In the early 1800s, A. M. Ampere first suggested the theory that magnetic fields were due to electric currents continually circulating within the atom.  Ampere's insight was pretty amazing considering the electron would not be discovered for another 75 years.