O ( ) are only used with polyatomic ions and only when there is more than one of any group. a. Examples: HNO 3. ) is incorrect; Al 2 ) 3 (SO 4

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1 HONORS CHEMISTRY - CHAPTER 9 CHEMICAL NAMES AND FORMULAS NOMENCLATURE PACKET - V16 NAME: DATE: PAGE: I. Writing formulas of ionic compounds when given the component parts. 1. Many compounds are composed of two parts, the first part being an element or polyatomic ion with a positive oxidation number and the second part being an element or polyatomic ion with a negative oxidation number. 2. The oxidation numbers should always add up to zero, if they do not, then subscripts are used to increase the number of ions/polyatomic ions until the total of the oxidation numbers equals zero. a. While crisscrossing the oxidation numbers usually works, remember that formula units must be written in simplest form. 1. Example: Sn(IV) + oxygen Initially produces Sn 2 O 4 However, the formula unit must be reduced to SnO 2 3. ( ) are only used with polyatomic ions and only when there is more than one of any group. a. Examples: HNO 3 is correct, H(NO 3 ) is incorrect; Al 2 (SO 4 ) 3 is correct, Al 2 SO 43 is incorrect. 4. If the cation, the element that has a positive oxidation number, has variable oxidation states (numbers), then the oxidation number to be used for this compound must be stated. Cu + O is incorrect ; it is unclear if Cu should be +1 or +2. Cu(II) + O is correct, this would yield CuO. 5. The Roman numerals found inside ( ) represent the oxidation state being used by the element in that compound; it never represents the number of atomsor ions of that element. a. Example: iron(iii) oxide is Fe +3 + O -2 Fe 2 O 3, not Fe +3 + O -2 Fe 3 O 2 1

2 II. Naming and Writing Formulas for Ionic Compounds 1. Ionic Compounds for Cations with One Oxidation Number: a. When naming ionic compounds we start with the cation: its name does not change. b. If the anion is a polyatomic ion: its name does not change. 1. Examples: AgNO 3 is silver nitrate, (NH 4 ) 3 PO 4 is ammonium phosphate, c. If the anion is an element (not a polyatomic ion): take the root of the name and add an -ide ending. 1. Examples: NaCl is sodium chloride, Al 2 O 3 is aluminum oxide. d. A few polyatomic ions, such as hydroxide and cyanide have the ending -ide as part of their normal name; when you see these words you must recognize them for what they are, do not confuse them as being an element whose "root" has gained the suffix -ide when writing a ionic compound. e. If the anion is a polyatomic ion that has one more oxygen atom than the normal -ate group, add the prefix per- to the polyatomic ion name. 1. Example: Since KClO 3 is potassium chlorate, then KClO 4 is potassium perchlorate. 2 - HC - Chapter 9 - Nomenclature Packet - V16

3 f. If the anion is a polyatomic ion that has one less oxygen atom than the normal -ite group, add the prefix hypo- to the polyatomic ion name. 1. Example: Since KClO 2 is potassium chlorite, then KClO is potassium hypochlorite. g. The prefix per- is only used with polyatomic ions that end in -ate; if it was used with polyatomic ions that ended in -ite, then it would equal the -ate group. 1. Example: The name for ClO 3 - is chlorate, not perchlorite. h. The prefix hypo- is only used with polyatomic ions that end in -ite; if it was used with polyatomic ions that ended in -ate, then it would equal the -ite group. 1. Example: The name for ClO 2 - is chlorite, not hypochlorate. i. The oxidation number of a group of related polyatomic ions is usually the same. 1. Example: ClO - (hypochlorite), ClO 2 - (chlorite), ClO 3 - (chlorate), ClO 4 - (perchlorate) all have a charge of one negative and an oxidation number of negative one. Polyatomic Ion Prefixes Polyatomic Ion Ending Prefix ate + an extra oxygen atom per ate ite ite - an oxygen atom hypo j. The central (first) atom in a polyatomic ion can be replaced by an element in the same family on the periodic table Examples: IO 3 is iodate and IO 4 is periodate. BrO 2 is bromite and FO - is hypofluorite, Again, all have a charge of one negative and an oxidation number of negative one. 3 - HC - Chapter 9 - Nomenclature Packet - V16

4 2. Ionic Compounds for Cations with More Than One Oxidation Number: a. The rules for the anion are the same as found in rule one above. b. For the cation: first determine what the oxidation state is; this should not be done by uncrisscrossing the oxidation numbers, instead use the number of atoms and oxidation number of the anion to calculate the oxidation number for each cation. 1. Example One: Calculate the oxidation number of the cation (Cu) being used in the compound CuO. Take the oxidation number of oxygen (-2) and multiply it by the number of oxygen atoms (1), this gives a total of -2. Since the total of all of the cations and anions must add up to equal zero, then the cations must have a total value of +2. Take that total and divide by the number of copper atoms (1) to equal the oxidation number for each copper atom being used in this compound (+2). 2. Example Two: Calculate the oxidation number of lead being used in the compound Pb 3 N 4. Take the oxidation number of nitrogen (-3) and multiply it by the number of nitrogen atoms (4), gives a total of -12. Since the total of all of the cations and anions must add up to equal zero, then all of the lead atoms must have a total value of +12. Take that total and divide by the number of lead atoms (3) to equal the oxidation number being used for lead in this compound (+4). 4 - HC - Chapter 9 - Nomenclature Packet - V16

5 3. Example Three: Calculate the oxidation number of tin being used in the compound SnO 2. Take the oxidation number of oxygen (-2) and multiply it by the number of oxygen atoms (2), this gives a total of -4. Since the total of all of the cations and anions must add up to equal zero, then the tin must have a total value of +4. Take that total and divide by the number of tin atoms (1) to equal the oxidation number being used for tin in this compound (+4). c. After the oxidation number for the cation is calculated, then the compound can be named using the Stock System. 1. Stock System: After the name of the cation the oxidation state is written in Roman numerals and placed inside ( ). a. Examples: In the compound PbS the lead has an oxidation number of +2, the compound can be named lead(ii) sulfide. In the compound Fe 2 O 3 the iron has an oxidation number of +3, the compound can be named iron(iii) oxide. 3. Naming compounds that are hydrates: a. They are named using all of the steps in rules one and two above, with the addition of the naming of the hydrate component. This is done by following the ionic name with the term hydrate to which the appropriate prefix has been added (See table below). The prefix signifies the number of molecules of water that are trapped in the crystal structure. Note: The dot that appears in the formula of a hydrate between the ionic name and the water molecules does not mean multiplication, it is simply used to separate the water molecules from the rest of the compound. Numerical Prefixes for Hydrates and Molecular Compounds Number Prefix Number Prefix 1 mono- 6 hexa- 2 di- 7 hepta- 3 tri- 8 octa- 4 tetra- 9 nona- 5 penta- 10 deca- 1. Examples: The compound Ba(OH) 2. 8H2 O is named barium hydroxide octahydrate. The compound CuSO 4. 5H2 O is named either copper(ii) sulfate pentahydrate or cupric sulfate pentahydrate. 5 - HC - Chapter 9 - Nomenclature Packet - V16

6 4. Naming compounds that have three parts: a. The first and third components follow the steps in rules one and two above for ionic compounds. The middle component, often hydrogen, may have a prefix if the third component has an oxidation number of negative three. 1. Examples: NaHSO 4 is named sodium hydrogen sulfate, no prefix is necessary because Na is +1, H is +1, and since SO 4 is -2 no other combination that would add up to zero. However, when the negative oxidation number is -3, more combinations are possible: KH 2 PO 4 is named potassium dihydrogen phosphate and K 2 HPO 4 is named potassium monohydrogen phosphate Since two combinations of potassium and hydrogen can add up to equal the -3 of the phosphate, the prefix for the hydrogen when there are two of them is used to clarify which compound is referred to. b. There is a second, older way, of naming these compounds. When only one hydrogen atom is the middle component it is not stated as such, instead the prefix bi- is placed in front of the last component. 1. Examples: KHSO 4, potassium hydrogen sulfate, is named potassium bisulfate; NaHCO 3, sodium hydrogen carbonate, is named sodium bicarbonate. 5. Naming compounds that have four parts: These compounds are named in almost the same manner as in rule four above, "Naming compounds that have three parts". In this case, there are simply two positive components before the hydrogen component. There are never any numerical prefixes in this type of compound as one of each of the positive components always adds up to the negative component. a. Example: LiKHPO 4 is named lithium potassium hydrogen phosphate or lithium potassium biphosphate. 6 - HC - Chapter 9 - Nomenclature Packet - V16

7 6. Naming molecular compounds, compounds composed of two nonmetals: a. Write the name of the element written first in the molecular formula; write the root of the name of the element written second and add an -ide ending. b. Ignore all oxidation numbers; there is no crisscrossing of oxidation numbers. Oxidation numbers only apply to ionic compounds. When writing the formula for a compound that is named using numerical prefixes, ignore the oxidation numbers of the elements; also, the prefixes are not crisscrossed. 1. Example: dinitrogen trioxide means two atoms of nitrogen and three atoms of oxygen, N 2 O 3, not N 3 O 2. c. The number of atoms of each element in the formula is stated by using a numerical prefix in front of each element's name (See table on page four above). However, if there is only one atom of the element, the prefix mono- is only used on the second element. Therefore, if there is no prefix on the first element, assume that there is only one of it. 1. Examples: N 2 O 5 is dinitrogen pentoxide; PCl 3 is phosphorus trichloride; CO is carbon monoxide. 7 - HC - Chapter 9 - Nomenclature Packet - V16

8 7. Naming acids: a. Determine if it is a binary acid (contains H and one other element) or a ternary acid (it contains more than two elements, that is H and a polyatomic ion). If it is a ternary acid go to step c, "Ternary acids", as found below. b. Binary acids: They are really just binary compounds that become acids when they are placed in water. Because of this, binary acids are to be named two ways: 1. The normal name: follow rule one, steps a and b, for ionic compounds (see above). 2. The acid name: use the prefix hydro-, the root of the name of the second element, the suffix -ic, and the word acid. The elements normally composing binary acids are: F, Cl, Br, I, S, Se, and Te. 3. Examples: HCl is called hydrogen chloride or hydrochloric acid, H 2 S is called hydrogen sulfide or hydrosulfuric acid. a. The acid name is more commonly used because these compounds are normally found in water. b. There is one polyatomic ion that is named as if it were a binary acid; HCN is called hydrogen cyanide or hydrocyanic acid. c. For a reason older than Mr. Harrison, HCl is also known as muriatic acid. 8 - HC - Chapter 9 - Nomenclature Packet - V16

9 c. Ternary acids: Ternary acids are also called oxyacids because the second component of the compound is a polyatomic ion that normally contains oxygen, are named based on the root of the name of the polyatomic ion according to the table found below. Ternary Acid Nomenclature Polyatomic Ion Ending Acid Prefix Acid Suffix ate + an extra oxygen atom per (r)ic ate (r)ic ite (r)ous ite - an oxygen atom hypo (r)ous d. Examples: HNO 3 is nitric acid, H 2 SO 3 is sulfurous acid, HClO is hypochlorous acid, HClO 4 is perchloric acid. Note: Organic chemists write the formula for acetic acid as CH 3 COOH, which is actually a type of condensed structural formula. However, we will use the inorganic method of writing the formula, HC 2 H 3 O 2,which makes it easier to recognize it as an acid. e. The suffixes -ic and -ous that are used for naming elements that have variable oxidation numbers also are used in naming ternary acids. Remember that an acid will always have the word acid at the end of the name. 9 - HC - Chapter 9 - Nomenclature Packet - V16