HONORS CHEMISTRY - CHAPTER 9 CHEMICAL NAMES AND FORMULAS OBJECTIVES AND NOTES - V18 NAME: DATE: PAGE: THE BIG IDEA: ELECTRONS AND THE STRUCTURE OF ATOMS. BONDING AND INTERACTIONS. Essential Questions 1. How does the periodic table help you determine the names and formulas of ions and compounds? 2. What is the difference between an ionic and a molecular substance? Chapter Objectives 1. Differentiate between ionic compounds (usually salts, sometimes bases) and molecular compounds, and between formula units and molecules. (9.1 & pp 201-203) 2. Identify and list the names and formulas of the common monatomic and diatomic molecules. (9.1) 3. Explain why a systematic method of naming chemical compounds is necessary. (9.2) 4. Write the chemical formula of an ionic compound when given the component parts of the compound. (9.2) 5. Write the chemical formula of a binary ionic compound when given the stock name of the compound. (9.2) 6. Name an ionic compound when given the formula of the compound. (9.2) 7. Write the chemical formula of a hydrate when given the chemical name(s) of the hydrate. (9.2 & pp 498 & 499) 8. Write the chemical name(s) of a hydrate when given the formula of the hydrate. (9.2 & pp 498 & 499) 9. Write the chemical formula of a binary molecular compound when given the name of the compound. (9.3) 10. Name a binary molecular compound when given the formula of the compound. (9.3) 11. Differentiate between and give examples of binary acids and ternary acids (oxyacids). (9.4) 12. Explain the properties of a binary molecular compound containing hydrogen and another nonmetal when anhydrous and when dissolved in water. (9.4) 1
13. Write the chemical formula of a binary molecular compound when given either the name of the anhydrous compound or the name of the binary acid. (9.4) 14. Write the names of a binary molecular compound containing hydrogen and another nonmetal when given the formula of the anhydrous compound or the formula of the binary acid. (9.4) 15. Write the chemical formula of a ternary acid (oxyacid) when given the name of the acid. (9.4) 16. Name a ternary acid (oxyacid) when given the formula of the acid. (9.4) 17. Using experimental data, show that different samples of the same compound obey the law of definite proportions. (9.5) 18. Using experimental data, show that two different compounds composed of the same two elements obey the law of multiple proportions. (9.5) 19. Demonstrate and be able to describe all aspects of laboratory safety rules and procedures. (Applicable every chapter) 9.1. Naming Ions 1. molecule: a. The smallest part of a molecular compound that maintains the properties of that compound. b. A single atom, or atoms of the same element bonded together, that can have a stable independent existence. 2. molecular compound: A compound composed of atoms. Molecular compounds are usually composed of nonmetals, that is, elements with negative oxidation numbers. a. Examples: water, carbon dioxide. 3. chemical formula: An abbreviation that expresses the composition of molecules and formula units in terms of chemical symbols and subscripts. a. Examples: H 2 O, NaCl, K 2 CO 3, CO 2, Ne, and H 2. 4. molecular formula: An abbreviation representing one molecule. It is composed of chemical symbols and subscripts that show the number of atoms of each element in the molecule. a. Examples: H 2 O, CO 2, Ne, and H 2. 2 - HC - Chapter 9 - Objectives and Notes - V18
5. monatomic molecule: A molecule composed of one atom. All of the examples are: helium-he, neon-ne, argon-ar, krypton-kr, xenon-xe, and radon-rn. 6. diatomic molecule: A molecule composed of two atoms. Note: This term is usually used as meaning homonuclear diatomic molecules, when both atoms are of the same element. All of the examples are: hydrogen-h 2, nitrogen-n 2, oxygen-o 2, fluorine-f 2, chlorine-cl 2, bromine-br 2, and iodine-i 2. These substances are diatomic when they are found free in nature at standard conditions; however, all of the elements that form (homonuclear) diatomic molecules can also be found chemically combined to other elements in forming compounds, i. e., oxygen is diatomic (O 2 ) when it is found by itself, it is just an element in the compound CO 2. 7. formula unit: The simplest whole number ratio of atoms or ions in a compound. It is usually used with ionic compounds. a. Examples: NaCl and Rb 2 Cr 2 O 7. b. See pp 201-203 in the textbook. A. Monatomic Ions 1. ion: 1. An atom or group of atoms that has lost or gained one or more electrons and thus carries an electrical charge. a. Examples: K +, F -, and PO 3-4. 2. cation: An ion with a positive charge. a. Examples: K +, Mg 2+, and NH + 4. b. The name for a monatomic cation is the same as the element name. 1. Examples: K + is the potassium ion and Sr 2+ is the strontium ion (Did you pronounce that as a Russian would?). 3. anion: An ion with a negative charge. a. Examples: F -, S 2-, and PO 3-4. b. The name for a monatomic anion is the same as the element, but it adds an ending of -ide. 1. Examples: F - is the fluoride ion and S 2- is the sulfide ion. 3 - HC - Chapter 9 - Objectives and Notes - V18
B. Polyatomic Ions 1. polyatomic ion: A group of atoms that has lost or gained one or more electrons and thus carries an electrical charge. They usually act as one particle. a. Examples: PO 3-4, OH -, and NH + 4. 9.2. Naming and Writing Formulas for Ionic Compounds A. Binary Ionic Compounds 1. ionic compound (salt): A compound composed of ions; yet, like a molecular compound, it has no overall charge. Ionic compounds are usually composed of a metal and a nonmetal, that is, a component with a positive oxidation number and a component with a negative oxidation number. Polyatomic ions with a positive charge can be used in place of the metal and ones with a negative charge can be used in place of the nonmetal. a. Examples: sodium chloride (NaCl) and calcium tartrate (CaC 4 H 4 O 6 ). 2. binary compound: A compound that is composed of two elements. a. Examples: NaCl and H 2 O. 3. binary ionic compound: An ionic compound that is composed of two elements. a. Examples: NaCl and Li 2 O. B. Compounds with Polyatomic Ions (Ternary Ionic Compounds) 1. ternary compound: A compound that is composed of three elements; usually it contains a polyatomic ion. a. Examples: K 2 SO 4 and Mg 3 (PO 4 ) 2. 2. anhydrous: Without water. 3. hydrate: A solid compound that contains molecules of water trapped in its crystal structure. In order to show that the water is attached to the compound a dot is placed between the water molecules and the rest of the formula. a. Examples: Na 2 CO. 3 H2 O and CoCl. 2 2H2 O; see pp 498 & 499 for the formulas of some other hydrates. 4 - HC - Chapter 9 - Objectives and Notes - V18
9.4. Naming and Writing Formulas for Acids and Bases 1. acid: A compound whose formula begins with hydrogen. This is really a terribly incomplete definition, but it will suffice for now. a. Examples: HCl, H 2 SO 4. b. Note: There are some exceptions to this rule; H 2 O and H 2 O 2 both begin with an "H", yet neither is normally not considered to be an acid. However, when in doubt, if a compound begins with an "H", it is probably an acid. 2. binary acid: An acid composed of hydrogen and usually one other element. Binary acids really aren t acids, they are binary molecular compounds found as gases at standard conditions. When they are placed in water they become acids. a. Examples: HCl and H 2 S. 3. ternary acid (oxyacid): An acid composed of hydrogen and usually two other elements; the second and third elements forming a polyatomic ion. a. Examples: H 2 SO 4 and H 3 PO 4. 9.5. The Laws Governing How Compounds Form 1. law of definite proportions/law of constant composition: Discovered by Joseph Proust in the early 1800 s. In a given chemical compound the elements are always combined in the same proportion by mass. a. H 2 O is always 2.02 g hydrogen for every 16.0 g oxygen, the ratio of the masses never varies. 2. law of multiple proportions: Discovered by John Dalton. When two elements combine to form a series of different chemical compounds, if the mass of one element is held constant, the mass of the other element always varies by the ratio of small whole numbers. a. In the compound H 2 O, the ratio of the mass of hydrogen to the mass of oxygen is 2.02 g to 16.0 g. To form another compound with hydrogen and oxygen, if the mass of the hydrogen was kept constant at 2.02 g, then the mass of the oxygen could be found to be 32.0 g. (This is the compound hydrogen peroxide, H 2 O 2,). Thus, the ratio of the oxygen varied by a factor of 2, a small whole number. b. This law, along with the law of definite proportions, supports the idea that atoms exist and that they combine in simple whole number ratios. 5 - HC - Chapter 9 - Objectives and Notes - V18