IONS AND IONIZATION

An ion is an atom or groups of atoms that carries an electric charge.
All atoms are made up of smaller particles, called subatomic particles. Some of these smaller particles carry and electric charge at all times, but the charges are not always apparent. The reason is that there are two different kinds of charges: positive and negative. The two sometimes balance each other inside the atom. This causes the atom to behave as though it carried no charge at all.

At the center of every atom is a nucleus, containing one or more particles called protons. Each of these protons has a posiive charge. Surrounding the nucleus are particles called electrons. Each of these has a negative charge.

An ordinary atom has exactly as many protons as electrons. This means that it has exactly as many positive charges as negative charges. All the charges balance, and the atom is electrical neutral.

Suppose you upset the balance by removing some of the particles. You will then produce en electric charge and form an ion. Thios process in ionization.

The particles removed are usually electrons. Protons are heavy particles in the nucleus. It is difficult to do anything to them. Electrons. However, are light particles, and some are bound rather lightly to the rest of the atom. They are easy to remove.

In fact, some electrons in atoms of metals are so easily removed that under certain condition they can be made to flow through the metal. We describe this as an electric current flowing through the metal. An electric current in emta; is actually the flowing of loose electrons.

It is possible to cause atoms to give up electrons by bombarding the atoms with energy in the form of light or heat. If an element cam be made to give off electrons when it is struck by light, those moving electrons will make up an electric currnt wherever they go. We can construct a photoelectric cell (or an “electric eye”) out of such elements.

A photoelectric cell is sometimes used to open and shut doors automatically. Light shining on the cells causes it to give of electrons. The electrons make up an electric current that causes the door to stay shut. As you approach the door, you body interrupts the beam of light. As a result, the electric current stops. The doors opens in time for you pass through.

Atoms will also realese electron is heated strongly enough. In a radio tube a metal wire is heated so that electrons are given off. The movement of these electrons can be strictly controlled because they carry negative charges. This means they can be attracted to any object that carries an negative charge. (Similar charges repel each other).

By controlling the flow of electrons in this fashion, we can make electric currents start and stop. We can direct them, strengthen weak currents, and so on. Instruments that make use of such controlled electron flows are electronic. Radio and television sets are common examples of electronic device.