Elements that have a full outer shell are inert in that they do not react with other elements to form compounds. They all appear in the far-right column of the periodic table: helium, neon, argon, etc. For elements that do not have a full outer shell, the outermost electrons can interact with the outermost electrons of nearby atoms to create chemical bonds. The electron shell configurations for 29 of the first 36 elements are listed in Table 2. Figure 2. Skip to content Chapter 2 Minerals.
Previous: Chapter 2 Minerals. Tell students that hydrogen is the simplest atom. It has only 1 proton, 1 electron, and 0 neutrons. It is the only atom that does not have any neutrons. Explain that this is a simple model that shows an electron going around the nucleus.
It shows the electron in the space surrounding the nucleus that is called an electron cloud or energy level. It is not possible to know the location of an electron but only the region where it is most likely to be.
The electron cloud or energy level shows the region surrounding the nucleus where the electron is most likely to be. This is a great question. This force is much stronger than the force of repulsion of one proton from another. Again, a detailed answer to this question is beyond the scope of middle school chemistry. But a simplified answer has to do with the energy or speed of the electron. As the electron gets closer to the nucleus, its energy and speed increases.
It ends up moving in a region surrounding the nucleus at a speed that is great enough to balance the attraction that is pulling it in, so the electron does not crash into the nucleus. Have students answer questions about the illustration on the activity sheet. Students will record their observations and answer questions about the activity on the activity sheet. Students can see evidence of the charges of protons and electrons by doing an activity with static electricity.
Note : When two materials are rubbed together in a static electricity activity, one material tends to lose electrons while the other material tends to gain electron. In this activity, human skin tends to lose electrons while the plastic bag, made of polyethylene, tends to gain electrons.
Hold the plastic strip firmly at one end. Then grasp the plastic strip between the thumb and fingers of your other hand as shown. The plastic will be attracted to your hand and move toward it. Students may notice that the plastic is also attracted to their arms and sleeves. Let students know that later in this lesson they will investigate why the plastic strip is also attracted to surfaces that have not been charged neutral.
Note : If students find that their plastic strip does not move toward their hand, it must not have been charged well enough. Have them try charging their plastic strip by holding it down on their pants or shirt and then quickly pulling it with the other hand.
Then they should test to see if the plastic is attracted to their clothes. If not, students should try charging the plastic again. Tell students that the plastic strip and their skin are made of molecules that are made of atoms. Tell students to assume that the plastic and their skin are neutral—that they have the same number of protons as electrons. Project the image Charged plastic and hand. Point out that before the students pulled the plastic between their fingers, the number of protons and electrons in each is the same.
Then, when students pulled the plastic through their fingers, electrons from their skin got onto the plastic. Since the plastic has more electrons than protons, it has a negative charge. Since their fingers gave up some electrons, their skin now has more protons than electrons so it has a positive charge. The positive skin and the negative plastic attract each other because positive and negative attract.
Explain to students why the plastic is attracted to the desk. The answer takes a couple of steps, so you can guide students by drawing or projecting a magnified illustration of the plastic and desk. After pulling the plastic between their fingers, the plastic gains extra electrons and a negative charge. The independence of electric charge from speed was proven through an experiment in which one fast-moving helium nucleus two protons and two neutrons bound together was proven to have the same charge as two separate, slow-moving deuterium nuclei one proton and one neutron bound together in each nucleus.
Electric charge is a property that produces forces that can attract or repel matter. Mass is similar, although it can only attract matter, not repel it. Still, the formula describing the interactions between charges is remarkably similar to that which characterizes the interactions between masses. For electric fields, the force F is related to the charges q 1 , q 2 and the distance r between them as:.
Both act in a vacuum and are central depend only on distance between the forces and conservative independent of path taken. However, it should be noted that when comparing similar terms, charge-based interaction is substantially greater than that based on mass. For example, the electric repulsion between two electrons is about 10 42 times stronger than their gravitational attraction.
Charge separation, often referred to as static electricity, is the building of space between particles of opposite charges. All matter is composed of atoms made up of negatively-charged electrons and positively-charged protons.
In the ground state, each atom is of neutral charge—its protons and electrons are equal in number, and it exists with no permanent dipole. Because electrons are labile i. Static Electricity : Due to friction between her hair and the plastic slide, the girl on the left has created charge separation, resulting in her hair being attracted to the slide. In chemistry, this charge separation is illustrated simply by the transfer of an electron from one atom to another as an ionic bond is formed.
In physics, there are many other instances of charge separation that cannot be written as formal chemical reactions. Consider, for example, rubbing a balloon on your hair. This is because electrons from one have transferred to the other, causing one to be positive and the other to be negative. Thus, the opposite charges attract. A similar example can be seen in playground slides as shown in. Charge separation can be created not only by friction, but by pressure, heat, and other charges.
Both pressure and heat increase the energy of a material and can cause electrons to break free and separate from their nuclei. Charge, meanwhile, can attract electrons to or repel them from a nucleus. Charge separation occurs often in the natural world. It can have an extreme effect if it reaches a critical level, whereat it becomes discharged. Lightning is a common example.
Dielectric polarization is the phenomenon that arises when positive and negative charges in a material are separated. The concept of polarity is very broad and can be applied to molecules, light, and electric fields. For the purposes of this atom, we focus on its meaning in the context of what is known as dielectric polarization—the separation of charges in materials. A dielectric is an insulator that can be polarized by an electric field, meaning that it is a material in which charge does not flow freely, but in the presence of an electric field it can shift its charge distribution.
Positive charge in a dielectric will migrate towards the applied field, while negative charges will shift away. This creates a weak local field within the material that opposes the applied field. Different materials will react differently to an induced field, depending on their dielectric constant. This constant is the degree of their polarizability the extent to which they become polarized.
The most basic view of dielectrics involves considering their charged components: protons and electrons. If an electric field is applied to an atom, the electrons in the atom will migrate away from the applied field.
The protons, however, remain relatively exposed to the field. This separation creates a dipole moment, as shown in. Reaction of an Atom to an Applied Electric Field : When an electric field E is applied, electrons drift away from the field.
On the molecular level, polarization can occur with both dipoles and ions. In polar bonds, electrons are more attracted to one nucleus than to the other. Water Molecule : Water is an example of a dipole molecule, which has a bent shape the H-O-H angle is When a dipolar molecule is exposed to an electric field, the molecule will align itself with the field, with the positive end towards the electric field and the negative end away from it.
Ionic compounds are those that are formed from permanently charge-separated ions. Ions are still free from one another and will naturally move at random. If they happen to move in a way that is asymmetrical, and results in a greater concentration of positive ions in one area and a greater concentration of negative ions in another, the sample of ionic compound will be polarized—a phenomenon is known as ionic polarization.
Electric charge is a physical property that is perpetually conserved in amount; it can build up in matter, which creates static electricity. This is a very unstable arrangement, and hydrogen gas undergoes a variety of reactions so as to reach a stable electron configuration where its energy level is either empty of electrons, or filled with electrons.
Atoms are at their most stable when their outermost energy level is either empty of electrons or filled with electrons. Sodium atoms have 11 electrons. Two of these are in the lowest energy level, eight are in the second energy level and then one electron is in the third energy level. This is a very unstable arrangement, and the element sodium is a highly reactive, deadly white semi-solid that will burst into flames on exposure to the air or will burn through human flesh on contact.
A reactive substance. Chlorine atoms have 17 electrons. Two in the lowest, eight in the second and 7 in the third energy level.
This too is a very unstable arrangement. This element is a gas at room temperature and was used in World War One as a poisonous attack weapon because of its high reactivity with human lungs.
These two atoms were made for one another.
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