As clothes rub together in the machine, electrons get knocked from one atom to another. The result is the all-too familiar static cling. Electricity and strong electric fields do a good job of creating ions think lightning. The neutral state of an atom is typically the most stable configuration unless molecular bonds and the chemical environment complicates the picture , so ions tend to discharge and return to their neutral state over time.
The reason for this is that, as an ion, the atom has a strong electric field that attracts the needed electron or the needed atom to take its extra electron. But once the atom becomes neutral, it has an equal number of electrons and protons, it does not have a very strong field, and therefore has little possibility of changing. Topics: atom , atoms , charge , electromagnetism , electron , electrons , ion , ionization , ionize , neutral atoms , proton , protons , static.
Atoms without an equal number of electrons and protons are more common than many people realize, such as the atoms found in table salt. 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. Use what you know about electrons and charges to explain why this happens. Each strip has extra electrons so they are both negatively charged. Because like charges repel, the pieces of plastic repelled each other. Explore Have students apply their understanding of protons and electrons to explain what happens when a charged balloon is brought near pieces of paper.
Materials for each group Inflated balloon Small pieces of paper, confetti-size Procedure Rub a balloon on your hair or clothes. Bring the balloon slowly toward small pieces of paper.
Expected results The pieces of paper will jump up and stick on the balloon. Ask students: What did you observe when the charged balloon was held near the pieces of paper? The paper pieces moved up and stuck on the balloon. The protons are tightly bound within the nucleus and not removable by ordinary measures. While the electrons are attracted to the protons of the nucleus, the addition of energy to an atom can persuade the electrons to leave an atom.
Similarly, electrons within atoms of other materials can be persuaded to leave their own electron shells and become members of the electrons shells of other atoms of different materials. In short, electrons are migrants - constantly on the move and always ready to try out a new atomic environment.
All objects are composed of these atoms. The electrons contained within the objects are prone to move or migrate to other objects. The process of an electron leaving one material object to reside perhaps only temporarily in another object is a common everyday occurrence. Even as you read the words of this web page, some electrons are likely moving through the monitor and adhering to your clothing assuming that you are using this resource online and wearing clothes. If you were to walk across the carpeting towards the door of the room, electrons would likely be scuffed off the atoms of your shoes and moved onto the atoms of the carpet.
And as clothes tumble in the dryer, it is highly likely that electrons on one piece of clothing will move from the atoms of the clothing onto the atoms of another piece of clothing. In general, for electrons to make a move from the atoms of one material to the atoms of another material, there must be an energy source, a motive , and a low-resistance pathway.
The cause and mechanisms by which this movement of electrons occurs will be the subject of Lesson 2. For now, it is sufficient to say that objects that are charged contain unequal numbers of protons and electrons.
Charged objects have an imbalance of charge - either more negative electrons than positive protons or vice versa. And neutral objects have a balance of charge - equal numbers of protons and electrons. The principle stated earlier for atoms can be applied to objects. Objects with more electrons than protons are charged negatively; objects with fewer electrons than protons are charged positively. In this discussion of electrically charged versus electrically neutral objects, the neutron has been neglected.
Neutrons, being electrically neutral play no role in this unit. Their presence or absence will have no direct bearing upon whether an object is charged or uncharged. Their role in the atom is merely to provide stability to the nucleus, a subject not discussed in The Physics Classroom. When it comes to the drama of static electricity, electrons and protons become the main characters. Like mass, the charge of an object is a measurable quantity. The charge possessed by an object is often expressed using the scientific unit known as the Coulomb.
Just as mass is measured in grams or kilograms, charge is measured in units of Coulombs abbreviated C. To illustrate the magnitude of 1 Coulomb, an object would need an excess of 6. And of course an object with a shortage of 6. The charge on a single electron is The quantity of charge on an object reflects the amount of imbalance between electrons and protons on that object.
There are specialized types of ions. Anions have more electrons than protons and so have a net negative charge. Cations have more protons than electrons and so have a net positive charge. Zwitterions are neutral and have both positive and negative charges at different locations throughout the molecule. Anions are generally larger than the parent molecule or atom, because the excess electrons repel each other and add to the physical size of the electron cloud. Cations are generally smaller than their parent atom or molecule due to the smaller size of their electron clouds.
Monoatomic ions are sometimes also represented by Roman numerals, which designate the formal oxidation state of the element, whereas the superscripted numerals denote the net charge. These representations can be thought of as equivalent for monoatomic ions, but the Roman numerals cannot be applied to polyatomic ions.
Ions can be formed by ionization, which is the process of a neutral atom losing or gaining electrons.
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