Naming Binary Compounds
RULES: 1. Determine which element is the cation; the cations are usually located toward the left of the periodic table. 2. Determine which element is the anion; the anions are usually located toward the right of the period table. 3. Write the cation first, using the name of the element. 4. Write the anion second, dropping the usual ending and replacing it with “-­‐ide.” NAMES OF THE COMMON ANIONS element name of anion element name of anion fluorine fluoride oxygen oxide chlorine chloride sulphur sulphide bromine bromide nitrogen nitride iodine iodide phosphorus phosphide Exercise # 1: Write the correct chemical name for each of the following: 1. KCl potassium chloride 10. BaCl2 barium chloride 2. MgO 11. AlCl3 3. LiF 12. K2S 4. NaBr 13. Na2O 5. CaO 14. K2O 6. AlN 15. Ca3P2 7. NaI 16. H2O 8. Al2S3 17. CaBr2 9. Ag3P 18. MgS Writing Chemical Formulae RULES: 1. Write the symbol of the cation on the left and the symbol of the 2.
3.
4.
5.
EXAMPLE FOR SODIUM NITRIDE: anion on the right. Write the charge of each ion by the upper right of each symbol. Cross the charges, ignoring the signs. Reduce to the “lowest common factor.” If the number beside an element is 1, do not write it. sodium nitride Rule 1 Na N Rule 2 Na1+ N3-­‐ Rule 3 Na3N1 Rule 4 Na3N Exercise # 2: Write the correct chemical formula for each of the following: Na1+O2-­‐ 1. sodium oxide Na2O 11. sodium fluoride 2. calcium chloride 12. boron nitride 3. magnesium sulphide 13. calcium hydride 4. silicon oxide 14. hydrogen oxide 5. aluminum carbide 15. calcium nitride 6. boron fluoride 16. aluminum nitride 7. potassium nitride 17. calcium oxide 8. cesium oxide 18. zinc iodide 9. aluminum bromide 19. barium silicide 10. calcium phosphide 20. silver oxide Suddenly, A Complication Arises! If the cation has more than one possible positive charge, we are in trouble. How do you name it? There are three different methods which we will investigate after we look at how you assign charges to atoms. Finding the Charge on an Atom RULES: 1. Find the charge of the anion. There is always only one negative charge. 2. Write the charge of the anion on the upper right hand corner of the molecule. 3. Multiply the number of anions by the charge of each anion. 4. To ensure that the molecule is neutral it must have as many positive charges as it has negative charges. Make sure that there are as many “+” as there are “-­‐“ 5. Determine the charge of the cation by dividing the total positive charges by the number of cations in the molecule. EXAMPLE FOR FINDING THE CHARGE ON THE Fe ION IN Fe2O3 Rule 1 the oxide ion has a 2-­‐ charge (found on the table above) Rule 2 Fe2O2-3 Rule 3 Fe2O2-3
2- × 3 =6-
Rule 4 there is a total charge of 6+ for the Fe ion Rule 5 Fe2O2-3
6+
2
= 3+
the charge on the iron ion was found to be 3+ Now we can start the hard part!!! Roman Numeral Method For Naming RULES: 1. Name the cation with its element name. Using the above example of Fe2O3 you would start with “iron”. 2. Write the Roman Numeral (I, II, III, IV or V) of the cation’s charge in brackets behind the cation name. Thus, the example becomes: “iron (III).” 3. Write the name of the anion with the “-­‐ide” ending as done before. The correct name for Fe2O3 is “iron (III) oxide. Exercise # 3: Write the correct Roman Numeral name for each of the following: 1. FeCl2 Fe2+Cl1-­‐ iron (II) chloride 4. Au2S3 2. Cu2O 5. Sb2O5 3. Hg3N 6. SnBr4 4. PbO2 7. AgCl 5. CuF2 8. CrBr3 Exercise # 4: Write the correct formula for each of these: 1. mercury (I) oxide Hg1+O2-­‐ Hg2O 6. tin (II) phosphide 2. lead (IV) chloride 7. gold (I) fluoride 3. iron (III) nitride 8. mercury (II) nitride 4. copper (I) sulphide 9. antimony (V) bromide 5. antimony (III) oxide 10. tin (IV) carbide “OUS/IC” Method for Naming RULES: 1. Name the cation using its “ous” or “ic” name. The “ous” ending refers to the lower cation charge. The “ic” ending refers to the higher cation charge. 2. Write the name of the anion as before with the “-­‐ide” ending. iron ferrous ferric 2+ 3+ gold aurous auric 1+ 3+ copper cuprous 1+ cupric 2+ antimony stibbous 3+ stibbic 5+ tin stannous stannic mercury mercurous mercuric Note: Zinc forms the 2+ ion and silver forms the 1+ ion 2+ 4+ 1+ 2+ lead plumbous plumbic phosphorus phosphorous phosphoric 2+ 4+ 3+ 5+ Exercise # 5: Write the correct “ous/ic” name for each of the following: 1. FeCl2 Fe2+Cl1-­‐ ferrous chloride 6. Au2S3 2. Cu2O 7. Sb2O5 3. Hg3N 8. SnBr4 4. PbO2 9. AgCl 5. CuF2 10. SbF5 Exercise # 6: Write out the correct chemical formula for the following molecules: 1. mercurous oxide Hg1+O2-­‐ Hg2O 6. stannous phosphide Sn3P2 2. plumbic chloride 7. aurous fluoride 3. ferric nitride 8. mercuric nitride 4. cuprous sulphide 9. stibbic bromide 5. stibbous oxide 10. stannic carbide Prefix Method for Molecular Compounds RULES: 1. This method is only used for binary compounds composed of two non-­‐metals. For practice purposes we will sometimes use this method for naming other compounds. 2. Count the number of atoms of each element in the compound. 3. Find the appropriate prefix from the list below, which you must memorize. 4. Place the appropriate prefix in front of the cation. 5. Place the appropriate prefix in front of the anion and write the “-­‐ide” ending, as before. 6. Do not write “mono” on the first element. 7. Watch out for exceptions. Exceptions for the Prefix Method 1. Peroxides (contain the O
2ion) 2
To write the formula for a peroxide, simply write the formula for the ordinary oxide and then ADD one oxygen atom. DO NOT REDUCE. Prefixes mono = 1 hexa = 6 di = 2 hepta = 7 tri = 3 octa = 8 tetra = 4 nona = 9 penta = 5 deca = 10 Examples CO2 carbon dioxide CO carbon monoxide PCl5 phosphorus pentachloride CBr4 carbon tetrabromide P2O3 diphosphorus trioxide sodium oxide: Na2O sodium peroxide: Na2O2 barium oxide: BaO barium peroxide: BaO2 hydrogen oxide: H2O hydrogen peroxide: H2O2 2. Diatomic Elements The molecules of these elements consist of two identical atoms. The do not occur as a single atom. Never, never, ever! F2 -­‐ fluorine(g) Br2 -­‐ bromine(l) N2 -­‐ nitrogen(g) H2 -­‐ hydrogen(g) Cl2 -­‐ chlorine(g) I2 -­‐ iodine(s) O2 -­‐ oxygen(g) Radicals You Need to Know phosphate (PO4)3-­‐ fluorate (FO3)1-­‐ ammonium (NH4)1+ sulphate (SO4)2-­‐ iodate (IO3)1-­‐ 2-­‐
carbonate (CO3) 1-­‐
nitrate (NO3) 1-­‐
chlorate (ClO3) bromate 1-­‐
(BrO3) 1-­‐
hydroxide (OH) 1-­‐
hydrogen carbonate (HCO3) 1-­‐
hydrogen sulphate (HSO4) 1-­‐
acetate (CH3COO) Naming Acid Salts A DIBASIC acid (one containing two hydrogen atoms like H2SO4) may not always lose all of its hydrogen atoms when forming a salt. The resulting salt, which contains hydrogen in its radical, is called an ACID SALT. Some common examples of such radicals; RADICAL VALENCE COMMON NAME PREFERRED NAME RADICAL (WITH CHARGE) -­‐HSO4 1-­‐ bisulphate hydrogen sulphate (HSO4)
1-­‐ -­‐HSO3 1-­‐ bisulphite hydrogen sulphite (HSO3)
1-­‐ -­‐HCO3 1-­‐ bicarbonate hydrogen carbonate (HCO3)
-­‐H2PO4 1-­‐ -­‐ dihydrogen phosphate (H2PO4)
-­‐HPO4 2-­‐ -­‐ monohydrogen phosphate (HPO4)
sodium hydrogen carbonate NaHCO3 sodium bicarbonate NaHCO3 calcium dihydrogen phosphate Ca(H2PO4)2 ammonium bisulphate NH4SO3 1-­‐ 1-­‐ 2-­‐ Some examples of such acid salts: HYDRATES Such compounds contain WATERS OF HYDRATION, a definite, chemically combined proportion of water. Some examples: copper (II) sulphate pentahydrate CuSO4•5H2O sodium sulphate decahydrate Na2SO4•10H2O magnesium sulphate heptahydrate MgSO4•7H2O BINARY ACIDS A compound of hydrogen and a halogen (group 7) or group 6 element is named by writing the word hydrogen followed by the name of the other element with the "-­‐ide" ending. For example; HBr is hydrogen bromide (when it is anhydrous or "without water"). Solutions of these compounds dissolved in water are acids. The WATER (aqueous) solutions are named by using the prefix "hydro-­‐", the stem of the name of the nonmetal element, and the ending "-­‐ic" followed by the word "acid". FORMULA NAME of ANHYDROUS COMPOUND FORMULA NAME OF AQUEOUS ACID HF(g) hydrogen fluoride HF(aq) hydrofluoric acid HCl(g) hydrogen chloride HCl(aq) hydrochloric acid HBr(g) hydrogen bromide HBr(aq) hydrobromic acid HI(g) hydrogen iodide HI(aq) hydroiodic acid H2S(g) hydrogen sulphide H2S(aq) hydrosulphuric acid