#1 Nomenclature Rev W10 KB WINTER 2010 Page 1 of 1

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1 CHEM& 151 NOMENCLATURE WINTER 2010 I. INTRODUCTION The naming of chemical entities is useful in a variety of applications. Directly, by knowing how to name chemical compounds you can begin to use the language of chemistry in your lecture discussions. This is vital to your ability to understand what is happening in a chemical process, and why learning to name chemical compounds is presented early in this course. In addition to lecture, as an experimental scientist, you will encounter chemical reagents when in working in the chemistry laboratory. These reagents are most often labeled by name, sometimes by symbol, or combination of the two. To be certain you are using the proper reagent, an understanding of chemical nomenclature is important. And, last but not least, outside of this class you use products every day that contain chemicals! You can directly apply your knowledge of naming chemical entities to what is in your environment. As a compliment to that, with the ever-present concern about what is being put into the environment, this knowledge can help in your awareness of the impact chemicals are having on the planet. In this experiment you will learn how to use the rules for naming inorganic compounds and will be asked to apply these rules to a number of examples. As you progress through this term and over the next several chemistry courses, you will become more proficient at naming chemical compounds. The key to this assignment is to become familiar with naming chemical compounds, not to have the rules memorized. Continue to review and practice naming and it will get easier over time. Many of the rules outlined in this handout and the textbook will make little sense until you begin to see the patterns in naming compounds. Thus, before you begin filling in the tables, read through most of this handout and use the rules provided to complete the lab. II. LEARNING OBJECTIVES After completing this exercise, you should feel comfortable with: Identifying the differences between ionic and covalent compounds by chemical name and formula Recognizing binary compounds from ternary compounds (ionic and covalent). Using IUPAC naming rules to name ionic and covalent compounds. Writing balanced chemical formulas based on the names of compounds. When to name compounds containing hydrogen cations as either ionic compounds or as acids. TO EARN YOUR FINAL STAMP: You may complete the entire assignment in lab, but the following reflects the minimum required to earn your final stamp: Complete the entire worksheet. You may work on the worksheet outside of the lab, however you MUST have completed all tables and all of the Hodgepodge items to get a stamp. A lab instructor will check over your lab worksheet when you get it stamped. REMEMBER: You must get a stamp from a laboratory instructor during lab time, before the due date! The lab stamp box can be found on the first page of the lab report sheet. #1 Nomenclature Rev W10 KB WINTER 2010 Page 1 of 1

2 III. INFORMATION/DISCUSSION As the field of chemistry evolved over time, it was clear that every chemical entity needed a unique chemical formula and a corresponding name. Because there were several ways compounds could be named, early chemists realized that a standardized procedure for naming was required. Thus, the IUPAC (the International Union of Pure and Applied Chemistry) was founded and one of its duties was to establish such a system. Today, chemical compounds are most often represented by their proper chemical title (IUPAC name), but in some cases a common or trade name is used instead of the accepted chemical name. Fortunately, very few of the common names are still used in the general chemistry laboratory. When these common names are presented, it would be prudent to get them memorized. In our discussion of naming we will need to consider two kinds of chemical bonds: Ionic and Covalent. In general, ionic bonding exists between a cation (positively charged ion) and anion (negatively charged ion) pair. Typically we find metal cations and nonmetal anions form ionic compounds. Many ionic compounds contain a collection of covalently bonded nonmetal atoms, called polyatomic ions in place of one or both of the ions. By contrast, molecular compounds contain only covalently bonded nonmetals, and are often referred to as covalent compounds. Within this definition exist molecular elements: a single type of nonmetal atom that exists in nature covalently bound as two or more elements as their basic units. This is different from atomic elements, which exist in nature as single atoms as their basic units. Most elements fall into the atomic element category. A. Naming Ionic Compounds For most classes of compounds, the more positive portion of the compound is represented first in the chemical formula. Typically, this would be a metal or positive polyatomic ion. The negative portion of the compound then follows in the formula (typically a nonmetal anion or negative polyatomic ion). Following this pattern, it would only make sense to name all ionic compounds as the positive portion first and the negative portion last. GENERAL RULE: For ionic compounds, write the name of the positive ion followed by the name of the negative ion. The IUPAC rules divide ionic compounds into two classes: binary compounds (consisting of two element types) and ternary compounds (consisting of three or more element types). Example: Binary compounds: Ionic: metal + nonmetal example: metal (Na, sodium) + nonmetal (Cl, chlorine chloride) NaCl sodium chloride example: metal (Ba, barium) + nonmetal (Cl, chlorine chloride) BaCl 2 barium chloride For the ionic compounds above, the sum of all ions (charges) in each compound formula is zero. That is, enough of each positive and negative ion were combined in each to form a neutral compound. Both sodium chloride and barium chloride are neutral compounds. The chemical formula, written correctly, tells us so. Helpful Hint: Unless a charge is written next to a chemical formula, assume the overall charge is zero. #1 Nomenclature Rev W10 KB WINTER 2010 Page 2 of 2

3 The ternary compound examples below illustrate the variety seen among ionic compounds. In the examples note the first contains metal cations (positive species) with negative polyatomic ion, the second example with a positive polyatomic ion with a negative polyatomic ion and last example having a positive polyatomic ion and a nonmetal anion (negative species). Example: Ternary compounds: Ionic: metal/ polyatomic cation + nonmetal/polyatomic anion example: sodium (Na +1 ) + phosphate ion (PO 4 3- ) Na 3 PO 4 sodium phosphate example: ammonium ion (NH 4 + ) + nitrate ion (NO 3 - ) NH 4 NO 3 ammonium nitrate example: ammonium ion (NH 4 + ) + chloride ion (Cl - ) NH 4 Cl ammonium chloride GENERAL RULE: Any ionic compound that contains at least one polyatomic ion will be a ternary compound. Helpful Hint: The Periodic Table of Elements is useful in predicting the charges of metals and nonmetals. Until you are familiar with the table, you need to be able to recall many atomic charges/oxidation states.* Likewise, getting familiar with names, formulas and charges of the polyatomic ions assigned by your instructor (many listed in Table 2) will also be important early on. *Refer to your textbook for a discussion on oxidation numbers and how it relates to charge. IUPAC Rules for Naming Ionic Compounds 1. Metal Containing Binary Compounds (only two elements) When a metal and a non-metal combine to form an ionic compound, the name for the compound consists of the name of the positive portion (metal) followed by the name of the negative portion. A. Positive portion (cation): metals or elements with a positive atomic charge/oxidation number (metals will always be positive). See Table 1 for a list. Type I: If the metal or element with the positive oxidation number has only one oxidation number possible, use the regular name of the element. Examples: Group IA (1A) metal ions all have a charge of +1 Group IIA (2A) metal ions all have a charge of +2 Group IIIA (3A) metal ions all have a charge of +3 Na always +1, named sodium Ba always +2, named barium Ga always +3, named gallium Type II: If the metal or element with the positive oxidation number has two or more oxidation states (i.e. divalent or multivalent) there are two methods for naming the positive portion (cation). 1. IUPAC Method - Use the element's regular name with the oxidation state written as a Roman numeral in parentheses following the name. (This is used with most transition elements and some heavier main group elements, such as mercury and lead) Example: copper (I) for Cu +1 and copper (II) for Cu +2 #1 Nomenclature Rev W10 KB WINTER 2010 Page 3 of 3

4 b. Common Name Method (for divalent metals)- Change the last syllable of the Latin name to -ous for the lower oxidation number or to -ic for the higher oxidation number. Example: copper becomes cuprous for Cu +1 and cupric for Cu +2 B. Negative portion (anion): nonmetals with a negative atomic charge/oxidation number. See Table 2 for a list. Typically Groups V, VI and VIIA (5A, 6A, and 7A): N 3-, O 2-, Cl -. The root name is typically the first syllable of the element name and the ending is replaced with ide. Example: oxygen becomes oxide bromine becomes bromide 2. Ternary Compounds (three or more elements) Ternary compounds are named in the same manner as binary compounds: name of the positive ion (cation) first and the negative ion (anion) last. Prefixes are not used to indicate multiple ions. A. For the positive portion use the same rules for metal ions as were used for the binary compounds (see 1A). For polyatomic cations, use their name (ex: NH4 + ammonium). B. Most polyatomic anions involve a central atom surrounded by some number of oxygen atoms. These are called oxoanions. Use the one of the following rules to name these anions. 1) For those with the lower oxidation number on the central atom (or a smaller number of oxygens), use the stem name of the central atom plus -ite for the ending syllable. 2) For those with the higher oxidation number on the central atom, use the stem name plus -ate for the ending syllable. Example: oxidation state polyatomic anion name S = +4 SO 3-2 S = +6 SO 4-2 sulfite sulfate 3) If a central atom exists in two or more polyatomic anions at the same oxidation state in combination with oxygen, use appropriate prefixes such as meta and ortho, or di, tri, tetra in front of the polyatomic ion names. You are expected to memorize only those indicated in class. Example: oxidation state polyatomic anion name Cr = +6 CrO 4-2 chromate -2 Cr = +6 Cr 2 O 7 dichromate Helpful Hint: The oxidation number for oxygen does not change in polyatomic oxoanions and is therefore left out of consideration. Oxygen uses the oxidation number of -2 for most compounds it s found in. #1 Nomenclature Rev W10 KB WINTER 2010 Page 4 of 4

5 4) If a central atom exists in several polyatomic anions at different oxidation states when combined with oxygen, use appropriate prefixes such as hypo and per in front of the polyatomic ion name. The following is an example for oxoanions of chlorine. Any of the group 7A elements would follow the same pattern. Example: oxidation state polyatomic anion name lowest oxidation # Cl = +1 ClO -1 hypochlorite lower oxidation # Cl = +3 ClO 2-1 higher oxidation # Cl = +5 ClO 3-1 highest oxidation # Cl = +7 ClO 4-1 chlorite chlorate perchlorate Helpful Hint: Ask you lecture instructor which polyatomic and oxoanions you are expected to memorize for class! Additional Examples: Cation + Anion Ca +2 calcium + ClO -1 hypochlorite Zn +2 zinc + CO -2 3 carbonate Fe +3 iron (III) + CrO -2 4 chromate K + potassium + PO 3-4 phosphate Na + sodium + H 2 PO - 4 dihydrogenphosphate Ionic Compound Formed (neutral) Ca(ClO) 2 calcium hypochlorite ZnCO 3 zinc carbonate Fe 2 (CrO 4 ) 3 iron (III) chromate K 3 PO 4 potassium phosphate NaH 2 PO 4 sodium dihydrogenphosphate B. Naming Covalent Compounds The IUPAC rules for naming covalent compounds uses the same binary and ternary classifications. In similar fashion, covalent names begin with the more positive nonmetal in the compound followed by the negative nonmetal in the compound formula. GENERAL RULE: For covalent compounds, the least electronegative atom is typically written first in the formula, and is the first element used in the compound name. Example: Covalent (molecular): nonmetal + nonmetal example: nonmetal (N, nitrogen) + nonmetal (O, oxygen oxide) NO 2 nitrogen dioxide example: nonmetal (N, nitrogen) + nonmetal (O, oxygen oxide) N 2 O 4 dinitrogen tetraoxide Helpful Hint: For covalent compounds there are no ions! We will learn how to predict which element will be more positive in a covalent compound as we learn more about the Periodic Table! For now, remember the first element listed is most likely the more positive one! Helpful Hint: One class of covalent compounds are the polyatomic ions! These groups of covalently bonded atoms carry an overall charge but they are NOT ionic! #1 Nomenclature Rev W10 KB WINTER 2010 Page 5 of 5

6 IUPAC Rules for Naming Binary Covalent Compounds 1. Non-metal Binary Compounds (two nonmetals combined, molecular and covalent) When two nonmetals form a binary compound, an additional step is used in naming: the number of atoms of each element is indicated using one of the Greek prefixes shown below. In the compound name, the first element (less electronegative) retains the element name. If only one atom of the first element is present, the name is unchanged (no prefix needed). If more than one of the first element is present, a numerical prefix is used before the element name. The second (more electronegative) element keeps the root portion of its name and ends in -ide. The second nonmetal ALWAYS gets a numerical prefix in the name, even if there is only one element present. Greek prefix: mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca- Number Example: CO carbon monoxide PCl 3 phosphorous trichloride N 2 O 4 dinitrogen tetroxide 2. Non-metal Ternary Compounds (more than two nonmetals combined) By in large, the only ternary compounds you will learn to name this term are acidic compounds, thus our discussion will shift on how to name acids. Organic compounds can also be ternary covalent compounds and have their own set of IUPAC naming rules. We will reserve our discussion of organic compounds until next term. Naming Compounds Containing Acidic Hydrogen(s). Acidic compounds as those compounds that start with hydrogen in the formula. Each carries two names depending on its physical state. In general, acidic compounds are named as acids ONLY when they are dissolved in water (i.e. aqueous solutions) and have (aq) after the formula. A. If the compound is binary (hydrogen and a non-metal), the -ide portion from the anion name changes to -ic and a hydro- precedes the root name for that non-metal element. In all acids, the word acid is part of the name notice the aq after the formula. Examples formula HX (g) HX (aq) HBr (g) HBr (aq) H 2 S (g) H 2 S (aq) name Hydrogen rootide Hydrorootic acid hydrogen bromide hydrobromic acid hydrogen sulfide hydrosulfuric acid #1 Nomenclature Rev W10 KB WINTER 2010 Page 6 of 6

7 B. If the compound is ternary (hydrogen and a polyatomic ion) and the anion name ends in - ite: if the species is a gas, hydrogen is added to the polyatomic ion name; if the species is aqueous, name the polyatomic ion, change the -ite to -ous, and add the word acid as a suffix. Examples formula H 2 SO 3 (g) H 2 SO 3 (aq) name hydrogen sulfite sulfurous acid C. If the compound is ternary (hydrogen and a polyatomic ion) and the name ends in ate for the anion: if the species is a gas, again add hydrogen in front of the polyatomic ion name. If the species is aqueous, change the -ate to -ic, and add the word acid as a suffix. Examples formula H 2 SO 4 (g) H 2 SO 4 (aq) name hydrogen sulfate sulfuric acid Additional examples: HClO 4 (aq) anion is perchlorate perchloric acid HClO 3 (aq) anion is chlorate chloric acid HClO 2 (aq) anion is chlorite chlorous acid HClO (aq) anion is hypochlorite hypochlorous acid HCl (aq) anion is chloride hydrochloric acid #1 Nomenclature Rev W10 KB WINTER 2010 Page 7 of 7

8 TABLE 1 COMMON CATIONS AND THEIR OXIDATION NUMBERS Group IA (1A) Group IIA (2A) Group IIIA (3A) Group IVA (4A) NH 4 + ammonium Cd 2+ cadmium Cu + copper (I) or cuprous Cu 2+ copper (II) or cupric Cr 3+ chromium (III) or chromic Co 2+ cobalt (II) or cobaltous Fe 2+ iron (II) or ferrous Co 3+ cobalt (III) or cobaltic Fe 3+ iron (III) or ferric Hg 2 2+ mercury (I) or mercurous ( + Hg Hg + ) Hg 2+ mercury (II) or mercuric Ni 2+ nickel (II) or nickelous Ni 3+ nickel (III) or nickelate Pb 2+ lead (II) or plumbous Pd 2+ palladium (II) or palladous Pb 4+ lead (IV) or plumbic Pd 4+ palladium (IV) or palladic Ag + silver Pt 2+ platinum (II) Pt 4+ platinum (IV) Sn 2+ tin (II) or stannous Sn 4+ tin (IV) of stannic Zn 2+ zinc #1 Nomenclature Rev W10 KB WINTER 2010 Page 8 of 8

9 TABLE 2 COMMON ANIONS, POLYATOMIC IONS AND THEIR OXIDATION NUMBERS Group VIIA (7A) Group VIA (6A) Group VA (5A) Br - bromide Cl - chloride O 2- oxide S 2- sulfide H - hydride Se 2- selenide N 3- nitride F - fluoride Te 2- telluride P 3- phosphide I - Iodide C 2 H 3 O 2 - acetate PO 3 3- phosphite H 2 PO 4 - dihydrogen phosphate HPO 4 2- hydrogen phosphate PO 4 3- phosphate HCO 3 - bicarbonate or hydrogen carbonate HSO - 3 bisulfite or hydrogen sulfite HSO - 4 bisulfate or hydrogen sulfate CO 3 2- carbonate CrO 4 2- chromate Cr 2 O 7 2- dichromate SO 3 2- sulfite SO 4 2- sulfate S 2 O 3 2- thiosulfate ClO - hypochlorite C 2 O 4 2- oxalate ClO 2 - chlorite ClO 3 - chlorate O 2 2- peroxide ClO - 4 perchlorate OH - hydroxide MnO - 4 permanganate NO - 2 nitrite NO - 3 nitrate SCN - thiocyanate CN - cyanide #1 Nomenclature Rev W10 KB WINTER 2010 Page 9 of 9

10 Final Lab Stamp here Lecture Instructor Turn in THIS page and all that follow for your lab report! Name Partner Date DRILLS: Formulas and Equations. Fill-in each blank in the table below with the formula of the neutral compound resulting when the cation at the left is combined with the anion at the top. Br -1 SO 4-2 NO 3-1 S -2 PO 4-3 H +1 K +1 Zn +2 Cu +2 Fe +3 Sn +4 DRILLS: Formulas and Equations. Fill-in each blank in the table below with the NAME of the neutral compound resulting when the cation at the left is combined with the anion at the top. Hydrogen containing compounds are to be named as acids. Br -1 SO 4-2 NO 3-1 S -2 PO 4-3 H +1 K +1 Zn +2 Cu +2 Fe +3 Sn +4 #1 Nomenclature Rev W10 KB WINTER 2010 Page 10 of 10

11 FILL-IN: Formula Writing and Compound Naming A. Name or write formulas for the following ionic compounds. Note: Please use the IUPAC rules and examples given in the discussion section on IONIC name and formula writing! 1. Ca 3 (PO 4 ) 2 2. AlBr 3 3. Iron (III) chloride 4. Ammonium dichromate 5. Mg(OH) 2 6. H 2 SO 4 (aq) 7. Pt(NO 3 ) 2 8. Barium bisulfate 9. CuF B. Name or write formulas for the following covalent (molecular) compounds. Note: Please use the IUPAC rules and examples given in the discussion section on COVALENT name and formula writing! 1. SO 3 2. Carbon dioxide 3. O 2 4. N 2 O 5. Phosphorus trichloride 6. N 2 O 5 7. CCl 4 8. Xenon hexafluoride 9. Iodine monobromide #1 Nomenclature Rev W10 KB WINTER 2010 Page 11 of 11

12 C. Hodgepodge: Fill-in each blank by writing symbols and formulas for the following atomic and molecular elements or ionic and covalent compounds: 1. Sodium bicarbonate 2. Oxygen molecule 3. Gold (I) nitrate 4. Calcium hypochlorite 5. Cl 2 (g) 6. Cupric dihydrogen phosphate 7. Lithium nitride 8. Pb 9. Zinc permanganate 10. Ag 2 C 2 O NH 4 Cl 12. CO 13. Iron (III) oxide 14. Perchloric acid 15. Na 3 PO Potassium acetate 17. Copper (II) bromide 18. Arsenic pentachloride 19. Nitrous acid 20. Hydrogen chlorate #1 Nomenclature Rev W10 KB WINTER 2010 Page 12 of 12