How to Measure Negative Ions

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Much of what is around you is far beyond your senses' ability to see or consciously detect. This refers not so much to the rich microbial life that exists practically everywhere on Earth but to what is in the air around you, or more to the point, what is the air around you.

Air consists of molecules, or groups of individual atoms representing different elements. Most of these are probably familiar to you: oxygen, carbon dioxide, methane and water vapor.

In addition to these electrically neutral molecules floating about are molecules that carry a net positive or negative electrostatic charge. These are called ions, and it can be handy to have an ion tester on hand to measure negative ions in particular; one everyday example is a household smoke detector.

What Are Ions?

Individual atoms consist of protons, which have a +1 charge; neutrons, which have no charge; and electrons, which have a -1 charge. The number of protons determines the element, or atom, type, and is usually about equal to neutron number. These tiny particles weigh about the same and lie at the atom's center, whereas electrons are essentially massless and "orbit" the center like planets around the sun.

A charged molecule consisting of different atoms (say, HCO3-) is also called an ion, even though only one of the atoms is responsible for the net charge. A molecule carrying a positive charge is called a cation, whereas a negatively charged ion is known as an anion. Ions result from an atom's "effort" to have exactly eight valence, or potentially shareable , electrons in its outermost orbital layer.

Any process that results in a given type of electrically neutral molecule (for example, Cl) gaining an electron is a negative ion generator because that process creates negatively charged ions (in this case, Cl-).

The Air Ion Meter

You may want to know the quantity of negatively charged ions (anions) zipping about in your environment because of information this can provide about the composition of the environment, e.g., whether it is safe for humans and animals. An air ion meter can accomplish this task.

These devices usually consist of two cylindrical capacitors, one inside the other. A capacitor is simply a component within an electrical circuit that can store charge (in the form of electrons). It is related to the circuit by the relationship Q = CV, where Q is the total charge and V is the voltage, or electrical potential difference.

An an air ion meter, the charges on the two cylindrical plates create an electric field between. When a negative ion enters the system, it is deflected toward the center capacitor by the direction of the electric field and is counted as it strikes an electrode there.

Negative Ions in the Solar System

One of the reasons for measuring the quantity and flow of ions in the environment is that the resulting information can reveal a great deal about the history of that environment. If you are talking about a room inside your parents' family home, that's not usually a big deal.

But it can be if you're taking about outer space instead.

The concentration of ions, negative and positive, can serve up a palette of useful data about the origin of celestial bodies, such as stars, planets and comets, with other objects in outer space. Human scientists can use an instrument called a plasma spectrometer to compare the level of negative ions (e.g., helium, argon, carbon and others) to those in Earth's own environment and propose conclusions about the respective "births" of objects like the moon, planets and asteroids.

References

About the Author

Kevin Beck holds a bachelor's degree in physics with minors in math and chemistry from the University of Vermont. Formerly with ScienceBlogs.com and the editor of "Run Strong," he has written for Runner's World, Men's Fitness, Competitor, and a variety of other publications. More about Kevin and links to his professional work can be found at www.kemibe.com.

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