LS: Speaking of Science Column February 16, 2009

What the electron does for energy

It can make compounds form. It can be used to provide the energy to heat and light your house. It can provide the energy to operate machinery and automobiles.

By moving between energy levels it can create light. By striking a metal target with sufficient energy it can create X-rays. What is it and where do we find it?

It is the electron.

The electron is one of three main components of the atom. The other two are the neutron and the proton. The protons and neutrons are tightly held in a very small dense center of the atom called the nucleus. There are many subatomic particles that have been identified that are also found in the nucleus.

The electrons are found around the nucleus and are mobile. They are attracted to the nucleus only by electrostatic attraction so are not rigidly attached to the nucleus.

Early theories of the atom had the electrons orbiting the nucleus in very definite well-defined orbits. As our understanding of atomic theory advances we came to believe that electrons surround the nucleus in an electron cloud with the electrons not confined to definite orbits.

They have certain energies and combinations of these energies collect around the nucleus.

The lower energy electrons will tend to be closer to the nucleus than the higher energy electrons.

The electrons are extremely small and one individual electron will not have much effect, but vast numbers of them can create all kinds of activity. For the rest of this article when I mention electrons I will be referring to the effect of multitudes of electrons.

Each atom attracts electrons to itself. This property is called electronegativity. As a rule metal atoms usually have a low electronegativiy so they have a loose hold on their electrons. Other atoms, nonmetals, have a higher electronegativity and hold tightly to their electrons. When an atom of low electronegativity comes in close proximity to an atom of high electronegativity one or more electrons are transferred to the higher electronegativity atom.

This results in one atom becoming a negative ion and the other a positive ion. These ions attract to each other by electrostatic attraction and form ionic bonds. Ionic solids are generally easily soluble in water.

If two atoms of similar higher electronegativities get close to each other a tug-of-war occurs for their electrons. The result is the atoms share the electrons forming a covalent bond. Covalent compounds are generally insoluble in water and tend to be stable at room temperatures.

An electron actually spins on its axis. Combined with the charge on the electron this forms a miniature magnet. Usually two electrons of opposite spin pair up and cancel the magnetic properties of each other. In some elements like Iron there are enough unpaired electrons that magnetic properties are imparted to the material. An electromagnet lines all the electrons along their spin axis making strong magnets.

If you take a conducting metal like copper, which loosely holds its electrons to its nucleus, and pass it through a magnetic field, the field pushes the electrons through the wire. As long as there is motion between the field and the wire a continuous current is made.

This current can be used to operate lights, motors, electronics and other devices. This current also can be strong enough to set up an electromagnetic force capable of levitating large objects such as trains. They can also set up opposing magnetic fields to form the braking system used on jumbo jets and high speed trains. Chemical reactions also can produce
electrons as in a battery forming a continuous current, as long as there are sufficient chemicals.

If an atom is “excited” by some external stimulus the electrons around the atom become energized and jump to higher energy levels. The electrons then return to their original state and in the process emit photons. Enough photons and you have visible light. Each atom has its own distinctive light spectra allowing astronomers to determine the composition of stars by studying the light spectrum of the stars.

Jack Costello taught in School District 51 for 37 years. The last 32 were at Fruita Monument High School, where he taught mainly physics and chemistry. He earned a master of science in education from the University of Utah.

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