This gives the balloon a negative charge. Since the sweater lost some electrons, it has more protons than electrons, so it has a positive charge. If you move the balloon toward the sweater, it will be attracted.
This is like moving the charged plastic strip toward the cloth it was rubbed on. You can also move the balloon toward the wall. The excess negative charge on the balloon repels negative charge on the surface of the wall.
This leaves more positive charge on the surface of the wall. The negatively charged balloon is attracted to the positive area on the wall. This is like moving the charged plastic strip toward the finger. Either do the following demonstration or show the video Balloon and Water.
The American Chemical Society is dedicated to improving lives through Chemistry. Skip Navigation. Lesson 4. Engage Show a picture of a pencil point and how the carbon atoms look at the molecular level. Project the image Pencil Zoom. Ask students questions such as the following: What are the three different tiny particles that make up an atom?
Protons, neutrons, and electrons. Which of these is in the center of the atom? Protons and neutrons are in the center nucleus of the atom.
You may want to mention that hydrogen is the only atom that usually has no neutrons. The nucleus of most hydrogen atoms is composed of just 1 proton. A small percentage of hydrogen atoms have 1 or even 2 neutrons. Atoms of the same element with different numbers of neutrons are called isotopes. These will be discussed in Lesson 2.
What zooms around the nucleus of an atom? Electrons Which one has a positive charge, a negative charge, and no charge? Proton—positive; electron—negative; neutron—no charge. The charge on the proton and electron are exactly the same size but opposite.
The same number of protons and electrons exactly cancel one another in a neutral atom. Show animations and explain that protons and electrons have opposite charges and attract each other. Project the animation Hydrogen Atom. Give each student an activity sheet. Explore Do an activity to show that electrons and protons attract each other.
Question to investigate What makes objects attract or repel each other? Materials for each group Plastic grocery bag Scissors Procedure, part 1 Charged plastic and charged skin Cut 2 strips from a plastic grocery bag so that each is about 2—4 cm wide and about 20 cm long.
Quickly pull your top hand up so that the plastic strip runs through your fingers. Do this three or four times. Allow the strip to hang down. Then bring your other hand near it. Expected results The plastic will be attracted to your hand and move toward it.
Explain Show students models comparing the number of protons and electrons in the plastic and skin before and after rubbing them together.
Explore Have students investigate what happens when a rubbed plastic strip is held near a desk or chair. Procedure, part 2 Charged plastic and neutral desk Charge one strip of plastic the same way you did previously.
This time, bring the plastic strip toward your desk or chair. Expected results The plastic moves toward the desk. Have students charge two pieces of plastic and hold them near each other to see if electrons repel one other. Ask students to make a prediction: What do you think will happen if you charge two strips of plastic and bring them near each other?
Procedure, part 3 2 pieces of charged plastic Charge two strips of plastic Slowly bring the two strips of plastic near each other. Expected results The strips will move away or repel each other. Ask students: What happened when you brought the two pieces of plastic near each other?
The ends of the strips moved away from each other. This means that the negative charge on an electron perfectly balances the positive charge on the proton. In other words, a neutral atom must have exactly one electron for every proton.
If a neutral atom has 1 proton, it must have 1 electron. If a neutral atom has 2 protons, it must have 2 electrons. If a neutral atom has 10 protons, it must have 10 electrons. You get the idea. In order to be neutral, an atom must have the same number of electrons and protons. This page was constructed from content via the following contributor s and edited topically or extensively by the LibreTexts development team to meet platform style, presentation, and quality:.
Learning Objectives Describe the locations, charges, and masses of the three main subatomic particles. Determine the number of protons and electrons in an atom. Define atomic mass unit amu. Electrons Electrons are one of three main types of particles that make up atoms. If an electron was the mass of a penny, a proton or a neutron would have the mass of a large bowling ball!
Protons A proton is one of three main particles that make up the atom. Neutrons Atoms of all elements—except for most atoms of hydrogen—have neutrons in their nucleus. Summary Electrons are a type of subatomic particle with a negative charge. Protons are a type of subatomic particle with a positive charge. Protons are bound together in an atom's nucleus as a result of the strong nuclear force.
Neutrons are a type of subatomic particle with no charge they are neutral. Like protons, neutrons are bound into the atom's nucleus as a result of the strong nuclear force. The nucleus is held together by the "strong nuclear force," which is one of four fundamental fources gravity and electromagnetism are two others. The strong force counteracts the tendency of the positively-charged protons to repel each other.
It also holds together the quarks that make up the protons and neutrons. Note: In addition to electrons and quarks, physicists have identified a number of other subatomic particles. Quantum physics describes the subatomic world as one that cannot be depicted in diagrams -- particles are not dots in space as depicted in this feature , but are more like "dancing points of energy.
0コメント