Chemical Bonds Section 3 Writing Formulas and Naming Compounds Scan Section 3 of your book, using the checklist below. Read all section titles. Read all bold words. Read all charts and graphs. Look at all the pictures and read their captions. Think about what you already know about chemical formulas and compounds. Review ion New oxidation number binary compound polyatomic ion hydrate Academic formula Formulate two questions about what you would like to learn. 1 What is an oxidation number? 2. What is a complex ion? Define ion. Use your book for help. an atom that has gained or lost electrons Define the following vocabulary words. Use your book for help. the number that tells how many electrons an atom gains, loses, or shares to become stable a compound made of two elements a charged group of atoms bonded together by a covalent bond a compound that has water chemically attached to its ions and written into its formula Define formula. Use a dictionary for help. a general fact, role, or principle expressed in math or symbols 222 Chemical Bonds
Writing Chemical Formulas SE, pp. 565 566 RE, pp. 328 329 Complete the table below for sodium and chlorine. Use the periodic table in your book. Element Oxidation Number Positive or Negative Charge? Sodium 1 positive Chlorine 1 negative Define what an oxidation number of 1 means. Accept all reasonable answers. An oxidation number of 1+ means that the element needs to gain one electron to become stable. SE, p. 567 RE, p. 330 Summarize the three steps in writing a formula for an ionic compound by completing the graphic organizer below. Accept all reasonable answers. 1. Write the symbol of the element or polyatomic ion that has the positive oxidation number or charge. Hydrogen, NH 4, and metals have positive oxidation numbers. 2. Write the symbol of the element or polyatomic ion with the negative oxidation number. Nonmetals other than hydrogen and polyatomic ions other than NH 4 have negative oxidation numbers. 3. The charge (without the sign) of one ion becomes the subscript of the other ion. Reduce the subscripts to the smallest whole numbers that retain the ratio of ions. Remember that the resulting compound is neutral in its charge. Chemical Bonds 223
Compounds with Complex Ions SE, pp. 569 570 RE, p. 331 Organize the steps for finding the formula for ammonium sulfate by completing the questions and answers below. Look at the Polyatomic Ions table in your book for help. Accept all reasonable responses. Question: What is the positive ion and its charge? Answer: The positive ion is NH 4 with charge 1. Question: What is the negative ion and its charge? Answer: The negative ion is SO 4 2 and its charge is 2. Compounds with Added Water SE, pp. 570 571 RE, p. 333 Question: Balance the charges to make the compound neutral. Answer: Two NH 4 ions ( 2) balance one SO 2 4 ( 2); the charge of one becomes the subscript of the other. Add parentheses for subscripts greater than one. The formula is: (NH 4 ) 2 SO 4 Summarize the information about hydrates by filling in the blanks below. Some ionic compounds have as part of their structure. A hydrate has water chemically attached to its ions and written into its chemical formula. The water can be removed from the hydrate crystals by them. The form of the compound without water is described as anhydrous. The formula CaSO 4 2H 2 O is named calcium sulfate dihydrate, whose common name is gypsum. The anhydrous form (without water), CaSO 4 is the common powder known as plaster of paris. water molecules heating 224 Chemical Bonds
Naming Binary Covalent Bonds SE, pp. 570 571 RE, pp. 333 334 Analyze eight different binary covalent compounds of your choice. Write the formula for each compound in the left column. Write out the name in the right column. Use the Prefixes for Covalent Compounds table in your book for help. Formula Name CONNECT IT Think of three common chemical compounds people use every day. Based on the rules listed throughout this section, write out the chemical formulas and chemical names of each one. water, H 2 O, or dihydrogen oxide; table salt, NaCl, sodium chloride; baking soda, NaHCO 3, sodium bicarbonate; baking powder, NaAl(SO 4 ) 2, sodium aluminum sulfate Chemical Bonds 225
Chemical Bonds Chapter Wrap-Up Now that you have read the chapter, think about what you have learned and complete the table below. 1. Write an A if you agree with the statement. 2. Write a D if you disagree with the statement. Chemical Bonds After You Read The properties of a chemical compound are the D SE p. 553 same as the properties of each element it contains. RE p. 312 An atom can gain or lose electrons in its A SE p. 558 outer shell. RE p. 318 Atoms can share electrons. A SE p. 561 RE p. 321 The oxidation number is the number of oxygen D SE p. 565 atoms in a molecule. RE p. 325 Compare your previous answers to these. Review Use this checklist to help you study. Review the information you included in your Foldable. Study your Science Notebook on this chapter. Study the definitions of vocabulary words. Review daily homework assignments. Re-read the chapter and review the charts, graphs, and illustrations. Review the Self Check at the end of each section. Look over the Chapter Review at the end of the chapter. SUMMARIZE IT about chemical bonds. After reading this chapter, list three things you learned 226 Chemical Bonds