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 on. In an attempt to simplify the concept and describe how some materials become magnetized, (for this <../Review/atom.jpg> exercise), 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 he depicted that electrons spin and orbit the nucleus of an atom much like planets in a solar system. It is not the only model of the atom, and it is just one theory of how atoms are structured.

In our exercise, the electron appears to orbit in the same path around the nucleus, but the Bohr Model shows that electrons do not really orbit in the same path, but change their orbit with each revolution. There are also later models of the atom that have built on Bohr's model to help explain more complex atoms.

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. The basic scientific principles of magnetism can be explained, nevertheless, 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 the center of an atom is what you observed. You should have concluded that the electrons spin as they orbit 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. A. M. Ampere first suggested the theory that magnetic fields were due to electric currents continually circulating within the atom in the early 1800s. Ampere's insight was pretty amazing considering it was not known for sure whether atoms existed in the early 1800s and the electron would not be discovered for another 75 years.