Molecules and Compounds

A group of two or more atoms forms a molecule. For instance, two atoms of hydrogen (H) form a hydrogen molecule (H2). When hydrogen unites chemically with oxygen, the result is water (H2O), which is compound. A compound, then consists of two or more elements. The molecule is the smallest unit of a compound with the same chemical characteristic. We can have molecules for either elements or compounds. However, atoms exist only for the elements.

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Elements

The combination of electrons and protons forming stable atomic structures result in different kinds of elementary substance having specific characteristics. A few examples are the elements hydrogen, oxygen, carbon, copper, and iron. An element is defined as substance that cannot be decomposed any further by chemical action. The atom is the smallest particle of an element that still has the same characteristics as the element. Atom itself is a Greek word meaning a particle too small to be subdivided. As an example of the fact that atoms are to small to be visible, a particle of carbon the size of a pinpoint contains many billions of atoms. The electrons and protons within the atom are even smaller.

Table lists some more examples of elements. These are just a few out of a total of 106. Notice how the elements are grouped. The metals listed across the top row are all good conductors of electricity. Each has an atomic structure with an unstable outside ring that allows many free electrons.

The semiconductors have 4 electrons in the outermost ring. This means they neither gain or lose electrons but share them with similar atoms. The reason is that 4 is exactly halfway to the stable condition of 8 electrons in the outside ring.

The inert gases have a complete outside ring of 8 electrons, which makes them chemically inactive. Remember that 8 electrons in the outside ring is a stable structure. An example is neon.

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Conductors, Insulators, and Semiconductors

When electrons can move easily from atom to atom in a material, it is a conductor. In general, all the metals are good conductors, with silver the best and copper second. Their atomic structure allows free movement of the outermost orbital electrons. Copper wire is generally used for practical conductors because it costs much less than silver. The purpose of using conductors is to allow electric current to flow with minimum opposition.

The wire conductor is used only as a means of delivering current produced by the voltage source to a device that needs the current in order to function. As an example, a bulb lights only when current is made to low through the filament.

A material with atoms in which the electrons tend to stay in their own orbits is an insulator because it cannot conduct electricity very easily. However, the insulators are able to hold or store electricity better than the conductors. An insulating material, such as glass, plastic, rubber, paper, air, or mica, is also called a dielectric, meaning it can store electric charge.

Insulators can be useful when it is necessary to prevent current flow. In addition, for applications requiring the storage of electric charge, as in capacitors, a dielectric material must be used because a good conductor cannot store any charge.

Carbon can considered a semiconductor, conducting less than the metal conductors but more the insulators. In the same group are germanium and silicon, which are commonly used for transistors and other semiconductor components.

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