Nonmetals, Inert Gases, and Semimetals

Transcription

1 Chapter 4 Elements and the Periodic Table Section 4 Summary Nonmetals, Inert Gases, and Semimetals Key Concepts What are the properties of nonmetals and inert gases? How are semimetals useful? Nonmetals are elements that lack most of the properties of metals. Most nonmetals are poor conductors of electric current and heat. Solid nonmetals are dull and brittle. Nonmetals usually have lower densities than metals. Except for Group 18, most nonmetals readily form compounds with other elements. Many metals and nonmetals react with each other. Because atoms of nonmetals usually gain electrons, electrons move from metal atoms to nonmetal atoms. Nonmetals can also form compounds with other nonmetals by sharing electrons. The elements in Group 14, the carbon family, can gain, lose, or share four electrons when reacting with other elements. Carbon is the only nonmetal element in the group. Carbon plays an important role in the chemistry of life. Group 15 is also known as the nitrogen family. The two nonmetals in the group are nitrogen and phosphorus. These nonmetals usually gain or share three electrons when reacting with other elements. Nitrogen is an element that occurs in nature as a molecule formed from two nitrogen atoms bonded together. A molecule that is made up of two atoms is a diatomic molecule. The elements in Group 16, the oxygen family, include three nonmetals oxygen, sulfur, and selenium. Atoms of these elements typically gain or share two electrons in a reaction. The oxygen you breathe is O 2. Ozone is O 3. The elements in Group 17 are known as the halogens. All but one of the halogens are nonmetals. A halogen atom typically gains or shares one electron when it reacts. In their elemental form, all of the halogens are very reactive. The elements in Group 18, the inert gases, do not ordinarily form compounds. That is because the atoms of these elements do not gain, lose, or share electrons. The inert gases tend to be unreactive. Hydrogen has the simplest and smallest atoms. Its atoms contain one proton and one electron. Some hydrogen atoms also contain neutrons. Because hydrogen s chemical properties are so different from the other elements, it cannot be grouped into a family. On the border between the metals and the nonmetals are seven elements called semimetals. The semimetals have some of the characteristics of metals and some of the characteristics of nonmetals. The most useful property of the semimetals is their varying ability to conduct electric current. Some semimetals are used to make semiconductors. Semiconductors are substances that under some conditions can carry electricity, and under other conditions cannot carry electricity. Semiconductors are used to make computer chips, transistors, and lasers. 78

2 Nonmetals, Inert Gases, and Semimetals (pp ) This section describes the properties of the elements in the periodic table that are not metals. Use Target Reading Skills As you read, complete the outline about nonmetals, inert gases, and semimetals. Use the red headings for the main ideas and the blue headings for subtopics when possible. Add supporting details. Nonmetals, Inert Gases, and Semimetals I. Properties of Nonmetals Physical Properties II. C. D. III. IV. V. 79

3 Nonmetals, Inert Gases, and Semimetals (continued) Properties of Nonmetals (pp ) 1. The elements that lack most of the properties of metals are called 2. Where are the nonmetals located on the periodic table? 3. Is the following sentence true or false? Four of the nonmetals are gases at room temperature. 4. Circle the letter of each sentence that is true about the physical properties of nonmetals. a. Solid nonmetals are brittle. b. They usually have lower densities than metals. c. Most are shiny. d. They are good conductors of both heat and electricity. 5. Except for the Group 18 elements, most nonmetals readily form Families With Nonmetals (pp ) 6. Circle the letter of the number of electrons that an atom in the carbon family can gain, lose, or share. a. 1 b. 4 c. 5 d All living things contain what kind of compounds? 8. Circle the letter of the number of electrons that an atom in the nitrogen a. 2 b. 7 c. 5 d The atmosphere is almost 80 percent 10. A molecule composed of two atoms is called a(n) 80

4 11. Circle the letter of the number of electrons that an atom in the oxygen a. 6 b. 7 c. 5 d Circle the letter of each sentence that is true about oxygen. a. The oxygen you breathe is a diatomic molecule. b. Oxygen rarely combines with other elements. c. Oxygen is the most abundant element in Earth s crust. d. Ozone (O 3 ) collects in a layer in the upper atmosphere. 13. Circle the letter of the number of electrons that an atom in the halogen a. 4 b. 1 c. 6 d Is the following sentence true or false? Uncombined halogens are dangerous to humans. Inert Gases (p. 154) 15. Circle the letter of each sentence that is true about the inert gases. a. They exist in large amounts in the atmosphere. b. They are chemically unreactive. c. They readily gain, lose, or share electrons. d. They are used in glowing electric lights. 16. Complete the table about families of nonmetals. Nonmetals Family Group Number Nonmetals in Family a. Carbon family b. Nitrogen family c. Oxygen family d. Halogen family e. Inert gases 81

5 Nonmetals, Inert Gases, and Semimetals (continued) Hydrogen (p. 154) 17. How many protons and electrons does a hydrogen atom have? 18. Why can t hydrogen be grouped in a family? Semimetals (p. 155) 19. What are semimetals? 20. What is the most common semimetal? 21. What is the most useful property of the semimetals? 22. What are semiconductors? 82