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# Wanderer: How Does Matter Become Electrically Charged?

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Source:
Author: Janice VanCleave

### Problem

How does matter become electrically charged?

### Materials

• masking tape
• 2 rulers
• 12-inch (30-cm) piece of string
• scissors
• sheet black construction paper, 12 inches × 16 inches (30 cm × 45 cm)
• marking pen
• 6 round labels with 3/8-inch (.95 cm) diameters, 2 different colors with 3 labels in each set

### Procedure

1. Tape one ruler to a table, with about 2 inches (5 cm) extending over the edge.
2. Tape one end of the string to the end of the ruler that is hanging over the table's edge.
3. Cut a circle with a 2-inch (5-cm) diameter (the measure of a line crossing a circle and passing through the circle's center point) from the black paper.
4. Tape the free end of the string to the edge of the paper circle.
5. Cut two 1-inch (2.5-cm) wide rings from the black paper. Make the diameter of one ring 6 inches (15 cm) and the diameter of the other ring 10 inches (25 cm).
6. Tape the rings to the string so that they are evenly spaced, with the paper circle hanging in the center of the rings.
7. Write a positive sign (+) on one set of three colored labels, and a negative sign (–) on the second set.
8. Affix all the labels with a positive sign on the paper circle, at random.
9. Place two labels with a negative sign on the inner ring and the remaining negative label on the outer ring, as in the diagram on page 4.

### Results

You have constructed a model of a lithium atom showing its electrical charges.

### Why?

There are only two known types of electric charges, positive and negative. A proton has a positive charge of + 1, and an electron has a negative charge of –1. Protons are found in the nucleus (center) of atoms, and electrons spin around the outside of the nucleus. Matter is anything that takes up space and has mass, such as gases, liquids, and solids. All matter is made up of atoms, which are the smallest part of an element that retains the properties of the element.

Lithium is one type of atom. The symbol for Lithium is Li. Lithium atoms, like all atoms, are electrically neutral. This means that the number of positive charges (protons) in the atom equals the number of negative charges (electrons). Electrons move in and out of fixed pathways outside the nucleus. These paths are represented by the "rings" in the lithium model. The "rings" vary in distance from the nucleus and are not confined pathways. They just indicate areas where electrons are most likely to be found.

### Let's Explore

1. What happens if the number of electrons in the electrically neutral lithium atom changes? A decrease or increase in the number of electrons changes any atom into an ion (a charged particle). Some atoms, such as lithium, tend to lose electrons. The electrons in the outermost part of the atom are held more loosely, and it is these electrons that are usually lost. When an atom loses an electron, the remaining number of electrons is less than the number of protons, and the atom becomes a positively-charged ion called a cation. Produce a model of a cation by repeating the activity using 1 less electron in the outer ring.
2. Atoms, such as Flourine, that tend to gain electrons take on a negative charge and are called anions. Prepare a model of an anion by using the procedure in the original activity, using 9 protons and 9 electrons in the atom, and add an extra electron to the outer ring for the anion. Science Fair Hint: Use models of the atoms and ions to prepare a poster showing the gain and loss of electrons in the formation of ions.
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