Whatsa Matter U. - Exploration

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Phriendly Physics Home - Background - Exploration

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Materials:

A collection of beads of three different colors - say, red, yellow and green. A piece of cardboard or other stiff surface, marked like so for each student. Also, a periodic table of the elements. Break the students up into groups of three each.

Information:

Remind the participants that protons have 1 positive charge and are pretty heavy; that neutrons have no charge and are pretty heavy, and that electrons have 1 negative charge and are pretty light. Remind them also that atoms have no net charge.

Hydrogen:

Hydrogen is the lightest element; it has only one proton in the nucleus. Stick a red bead on the nucleus. But to keep it neutral, there has to be an electron. It can go on any dot, but it usually on one of the dots closest to the proton. Stick a green bead on the inner circle. Why is the electron close to the proton? Because opposites attract!

Helium:

Helium is the next lightest element; it has two protons in the nucleus. Stick a second red bead on the nucleus. But if you look on the periodic table, you see that the mass is four, not two. So there have to also be two neutrons. Stick two yellow beads in the nucleus. Now to keep it neutral, there have to be two electrons. We already have one, and we need another. Again, it can go on any dot, but it usually on one of the dots closest to the protons. Stick another green bead on the inner circle.

Lithium:

Who's next? Lithium! Have the participants work this one out from the table alone. (They might not be familiar with this element.) They should get 3 reds, 4 yellows, and 3 greens.

Other Elements:

Riddle time! Work out the bead arrangements for the following:

• "You see me in the window at the stores"
• "They put me in the water at the swimming pool"
• "It's in your pencil lead but it isn't lead"
• "Most of what you breathe every day"

Oxygen:

The last riddle is: "Why you need to breathe" and leads the participants to create oxygen. Now have them notice that there are two empty spots in the second ring. Have two of the participants in each group try to recreate hydrogen, and then have all three put their cards next to each other. If the atoms are close enough together, the electrons from the hydrogen can jump into the oxygen and back very quickly, and this will hold the hydrogen atoms onto the oxygen atom. Q: What are they are looking at? What is that called?