Figure 1. Composition of Matter

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A still more complex atom, shown in figure 1, is the atom of lithium, a

light, soft metal. Note that a third proton has been added to the nucleus

and that a third electron is now circling around the nucleus.

There are

also two additional neutrons in the nucleus; these are needed to hold the

three protons together.

The atoms of other elements can be analyzed in a similar manner.

As the

atomic scale increases in complexity, protons and neutrons are added one by

one to the nucleus and electrons to the outer circles or shells, as they are

termed by scientists. After lithium comes beryllium with four protons and

five neutrons, boron with five protons and five neutrons, carbon with six

and six, nitrogen with seven and seven, oxygen with eight and eight, and so

on.

In each of these, there are normally the same number of electrons

circling the nucleus as there are protons in the nucleus.

b. Composition of Electricity. When there are more than two electrons

in an atom, they will move about the nucleus in different size shells. The

innermost shells of the atom contain electrons that are not easily freed and

are referred to as bound electrons. The outermost shell will contain what

are referred to as free electrons (see figure 2 on the following page).