Name ___________________________________ Date ______________________ Class ______________________ Chapter 9 – Chemical Names and Formulas Naming Compounds Naming Ions For metal ion: use the element name with the word “ion” written after it. The word “ion” MUST be included to distinguish the ion from the element Examples: Na+1 sodium ion Ca+2 calcium ion Al +3 aluminum ion For nonmetal ions: the element name is given an –ide ending. Examples: C-4 carbide ion F-1 fluoride ion Ion Name lithium ion magnesium ion sodium ion carbon ion boron ion Ion Symbol Ion Symbol N-3 O-2 Au+1 C-4 I-1 Br-1 bromide ion Ion Name Naming Binary Ionic Compounds When Given the Chemical Formula **For naming binary ionic compounds, write the name of the cation first, then write the name of the anion using the –ide ending. The word “ion” is not used when writing compound names. Also, no reference is made to any numerical subscripts that may be in the formula. Examples: NaCl sodium chloride Na3N sodium nitride CaCl2 calcium chloride Formula KF BaS Li2O ZnCl2 Ba3N2 Compound Name Formula CaO Al2O3 Mg3P2 Na2N CaBr2 Compound Name Writing Binary Ionic Formulas When Given the Compound Name When writing formulas for binary ionic compounds, first write the ions with the correct charges. Then write the element symbols without the charges, placing the metal first. Now balance the electrical charges. The net charge on the compound must be zero. (Ask yourself: how many positive charges are needed to balance the negative charges?) **For any ionic compound, the total number of positive charges MUST balance the total number of negative charges. The net charge MUST be zero. First, write the ion symbol over the name of each ion. (This will help you learn the names and correct formulas for each of the ions!) Then write the correct formula. Examples: Na+1 Cl-1 Ba+2 F-1 K+1 O-2 Sodium chloride NaCl Barium fluoride BaF2 Potassium oxide K2O Compound Name calcium phosphide magnesium oxide barium nitride aluminum phosphide Formula Compound Name potassium chloride lithium fluoride sodium sulfide silver chloride Formula Most of the transition metals and some of the metals in groups 13, 14, 15 and 16 can form ions with more than one charge. This variation in charge occurs because the transition metal atoms may use one or more of their d sublevel electrons as a valence electron, or, in the case of metals in groups 13-16, sometimes only the p sublevel valence electrons are lost. The following are examples of metals that form ions having more than one charge. Only the more common charges have been given here (some may form ions having other charges). You have a sheet with this information also. Fe2+ Fe3+ Pb2+ lead (II) ion Pb4+ lead (IV) ion iron (II) ion iron (III) ion Mn2+ Mn3+ manganese (II) ion manganese (III) ion Naming Compounds Containing Ions That Have More Than One Charge To name such compounds, simply follow the rule for naming binary ionic compounds: name the cation first, then name the anion. The only difference is that you MUST include the Roman numeral for the charge of the cation. Remember that the anions have fixed charges. Example 1: In the formula MnO, the manganese ion has a +2 charge and the oxide has a -2 charge. The compound is called manganese (II) oxide. Example 2: In the formula CuS, the copper ion has a charge of +2 (there is only one copper ion and there is one sulfide ion with a charge of -2, so the copper ion must have a charge of +2). The compound is named copper (II) sulfide. Formula MnO PbO2 Fe2O3 Cu3P2 SnF2 Compound Name Writing Formulas for Ions That Have More Than One Charge To write the formula when given the name of a compound, write the symbol for each ion above its name first. Then write a balanced formula. Example: Cu+2 S2Cu+1 S-2 Copper (II) sulfide CuS Copper (I) sulfide Cu2S Compound Name copper (I) oxide lead (II) chloride Cobalt (II) chloride mercury (II) bromide mercury (I) oxide Formula Compound Name iron (II) oxide lead (IV) oxide cobalt (III) chloride mercury (I) bromide mercury (II) oxide Formula As the name suggest, polyatomic ions contain many atoms. A polyatomic ion is an ion consisting of two or more atoms chemically bonded together by covalent bonds and carrying a net electric charge. Remember the definition of an ion: an atom or molecule that has gained or lost one or more valence electron and has become a charged particle. Polyatomic ions are molecules that have become ions. Almost all polyatomic ions carry a negative charge. The original molecules have gained electrons. The exception is the ammonium ion, NH41+. The ammonium ion is a polyatomic ion that carries a positive charge. The ammonium ion is formed when an ammonia molecule, NH3, forms a coordinate covalent bond with a hydrogen ion, H+1. The ammonia molecule doesn’t lose electrons but rather gains a positively charged particle: the single proton of the hydrogen ion. It is this “additional” proton – or rather the additional positive charge – that gives the ion its 1+ charge. Writing Formulas Containing Polyatomic Ions The polyatomic ion behaves as a SINGLE UNIT. Treat the formula of a polyatomic ion as you would an ion of a single atom. Remember, the total number of positive charges must equal the total number of negative charges. There is a zero net charge on the ionic compound. NEVER CHANGE THE FORMULA OF A POLYATOMIC ION: DO NOT OMIT OR CHANGE ANY SUBSCRIPT IN THE FORMULA!! Example 1: Na+1 + SO4-2 there is one positive charge and one negative charge; therefore, only one of each ion is required: NaOH. Notice that the symbols of the ions involved are written with no space between them writing Na OH is incorrect. Example 2: Na+1 + SO4-2 there is one positive charge, but there are two negative charges; therefore, two positive ions are needed to balance the negative charges: Na2SO4. Again, notice the placement of the symbols of the ions and subscript. The formula is not written Na2 SO4. Be very careful when writing formulas of compounds. So far so good; But in the examples above, only one polyatomic ion was involved. How do we write the formula of a compound that requires MORE than one polyatomic ion? Figure out how many total positive and total negative charges are needed, and how many of each ion are needed. Then use parentheses () around the entire polyatomic formula and write the necessary subscript OUTSIDE the parentheses. Example 1: Ca2+ + OH-1 required: Ca(OH)2. Here we have two positive charges and only one negative charges. Two negative ions are Example 2: Al3+ + OH-1 Al(OH)3. Here we have three positive charges and one negative charge. Three positive ions are needed: And what do we do if the positive ion is a polyatomic ion and the negative ion is also a polyatomic? NOTHING DIFFERENT!! Use parentheses!! Just remember to treat the polyatomic ions as single units. Example 1: NH4+1 + OH-1 only one of each ion is needed: NH4OH. Example 2: NH41+ + CO32- two ammonium ions are needed to balance the charge on the carbonate ion: (NH4)2CO3. OH-1 Li+1 NH4+1 Pb+2 Fe+3 NO3-1 SO4-2 PO4-3 C2H3O2-1 Writing Names from Formulas Containing Polyatomic Ions Now that you can write the formulas of compounds containing polyatomic ions, let’s try naming the compounds from the formulas. And then we’ll write formulas from the names of compounds. Name each ion in the formula. Do not include any reference to the subscripts either in the polyatomic ion formula or in the compound formula. Examples: NaOH is sodium hydroxide (NH4)2S is ammonium sulfide Formula LiOH FeSO4 NH4F (NH4)3PO4 Co(OH)2 Pb(OH)4 is lead (IV) hydroxide Compound Name Compound Name sodium sulfate copper (I) phosphate barium hydroxide iron (II) phosphate magnesium phosphate Formula Compound Name potassium hydroxide copper (II) phosphate ammonium carbonate iron (III) sulfate ammonium phosphate Formula Writing Names and Formulas for Molecular Compounds: Molecular compounds are composed of two or more nonmetals, and do NOT contain ions. Examples: sulfur dioxide, SO2 carbon dioxide, CO2 sulfur trioxide, SO3 dihydrogen monoxide, H2O carbon monoxide, CO2 glucose, C6H12O6 As you can see, very often, Greek prefixes are used in the names of compounds having more than one atom of a given element. The general rules for naming binary (having two elements) molecular compounds are: 1. If there is only one atom of the first element, no prefix is used: Examples: CO, carbon monoxide SO3, sulfur trioxide ClO7, chlorine heptoxide 2. If there are two or more atoms of the first element, the appropriate prefix is used. Examples: N2O, dinitrogen monoxide P2O5, diphosphorus pentoxide 3. For the second element, a prefix is always used to indicate the number of atoms present; -ide ending is used for the second element. Examples: see examples given for rules 1 and 2. Common prefixes and their meanings: mono- (one) di- (two) tri- (three) tetra- (four) penta- (five) hexa- (six) hepta- (seven) octa- (eight) nona- (nine) deca- (ten) HINT: The final vowel in a prefix is often dropped before a vowel in a stem word: mono- and oxide become monoxide; tetra- and oxide becomes tetroxide. Formula N 2O N 2O 5 PCl5 N 2O 4 PCl3 Compound Name dichlorine monoxide chlorine trifluoride sulfur hexafluoride Compound Name Formula Compound Name chlorine dioxide chlorine heptoxide dihydrogen monoxide Formula An acid is a compound that produces H+ ions in an aqueous (water) solution. A base is a compound that produces OHions in an aqueous solution. Naming Acids Acids not containing a polyatomic ion (or oxygen) are named by using hydro- plus the root of the anion plus –ic plus acid. Acids containing oxygen are named by using the polyatomic root plus –ic if the original polyatomic name contained –ate or plus –ous if the original root was –ite. If there is sulfur in the polyatomic –ur is added before the –ic or –ous. If there is a phosphorus in the polyatomic –or is added before the –ic or –ous. These are summarized below. 1. 2. 3. 4. 5. If no oxygen: hydro + anion root + ic + acid (example – HCl is hydrochloric acid). If oxygen present: polyatomic root + ic (replacing –ate ending) + acid (example HClO3 – chloric acid). If oxygen present: polyatomic root + ous (replacing –ite ending) + acid (example HClO2 – chlorous acid). If sulfur present: polyatomic root + ur + ic/ous + acid (example H2SO4 – sulfuric acid). If phosphorus present: polyatomic root +or + ic/ous + acid (example H3PO4 – phosphoric acid). Formula HBrO H2CO3 HCl H3PO3 HF Compound Name Writing Formulas for Acids To write the formula for an acid look at the name. Reverse the process and change the endings to find out which root anion or polyatomic ion you are dealing with. Next, balance the negative charges with hydrogen. Example 1: periodic acid…root polyatomic would be periodate or IO41- so balance that with hydrogen to get HIO4. Example 2: thiosulfuric acid…root polyatomic would bethiosulfate or S2O32- so balance that with hydrogen to get H2S2O3. Compound Name hydrosulfuric acid nitric acid bromous acid sulfuric acid thiosulfuric acid Formula Compound Name chromic acid hydroiodic acid nitrous acid perchloric acid dichromic acid Formula Naming Bases A base is composed of a metal and an OH- ion. You name the metal and then the OH- with hydroxide. Ammonia, NH3 is a base. When ammonia is put into water it forms ammonium, NH4 and gives off OH- ions. NH3 + H2O → NH4+ + OH-. Examples: NaOH is sodium hydroxide Formula KOH Fe(OH)2 Al(OH)3 Mg(OH)2 LiOH Fe(OH)3 is iron (III) hydroxide Compound Name Writing Formulas for Bases To write the formula for bases simply write the formula like you would for an ionic compound. Write the formula for the metal ion, using Roman numerals where needed, then the formula for hydroxide. Balance the formula and you’re done. Compound Name zinc hydroxide iron (III) hydroxide chromium (II) hydroxide beryllium hydroxide calcium hydroxide Formula Compound Name silver hydroxide nickel (II) hydroxide sodium hydroxide aluminum hydroxide copper (III) hydroxide Formula Name ___________________________________ Date ______________________ Class ______________________ Prefixes: 1 = mono 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa 7 = hepta 8 = octa 9 = nona 10 = deca Roman numerals: 1 = I 6 = VI 2 = II 7 = VII 3 = III 8 = VIII 4 = IV 9 = IX 5 = V 10 = X START HERE Is the compound an acid? to write formulas NO YES Work the ending backward then balance with hydrogen. Does the compound have prefixes? NO YES The compound is ionic. More information is needed The compound is molecular . 1) Does the name have Roman numerals? 2) Does the name have polyatomic ions? (think -ate or -ite endings) 3) No Roman numerals or polyatomic ions Roman numeral gives charge on metal cation. Use the polyatomic ion chart for formula and charge. Use the periodic table (of ions) for charges Balance charges using criss cross method (using parenthesis if needed) Use the prefixes to write the name. - ide hydro__ic acid -ate __ic acid -ite __ous acid Prefixes: 1 = mono 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa 7 = hepta 8 = octa 9 = nona 10 = deca Roman numerals: 1 = I 6 = VI 2 = II 7 = VII 3 = III 8 = VIII 4 = IV 9 = IX 5 = V 10 = X START HERE Is the first element hydrogen (H)? to write names NO YES Are there more than two elements? NO The compound contains a polyatomic ion - usually ends in -ate or -ite Is the first element a metal? Does the cation need a Roman numeral? (look for split boxes on the periodic table) Find the anion name and change the ending - ide hydro__ic acid YES Does the cation need a Roman numeral? (look for split boxes on the periodic table) NO Use prefixes to name YES The compound is binary - name ends in -ide NO The compound is binary covalent The compound is an acid Name the ions - cation first then anion. YES NO Name the ions - cation first then anion. Name the ions using Roman numerals for the metal cation. -ate __ic acid -ite __ous acid YES Name the ions using Roman numerals for the metal cation.