Nomenclature of inorganic compounds. = naming non carbon (mostly) compounds. Some definitions:

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1 1 Chemistry 047 Inorganic Nomenclature Nomenclature of inorganic compounds = naming non carbon (mostly) compounds Some definitions: Nomenclature = system used by chemists to name and identify compounds Common names = based on chemical or physical characteristics but not based on composition used by lay people either easier or proper name too long used for industry Systematic names = chemical nomenclature that describes chemical characteristics and identifies chemical composition IUPAC = International Union of Pure and Applied Chemistry they revised systematic names and created rules for naming compounds I. Elements and Ions A. Elements (reminder) Names are represented by symbols (listed on periodic table) Atoms uncharged (neutral atom) so = # protons = # of electrons The element is defined by # of protons it contains B. Diatomic and polyatomic molecules These molecules are not found as single atoms at normal temperatures in their free state always found as 2 of the atoms bonded together di =2 7 elements are diatomic = H, N, O, F, Cl, Br, I (acronym N,O, Hal +H - Halogens = Hal they don t know much about astatine (the last Halogen) as it is extremely unstable and only seems to exist for up to 8 hours they now think it is not found in diatomic state so don t include) 2 other elements are found in polyatomic state (poly= more than 2) S8 sulfur and P4 phosphorus C. Ions = Anions and Cations Ions = charged particles - produced by adding or taking away electrons from a neutral atom Charge can be predicted from its position on the periodic table Page 1 of 9

2 2 Chemistry 047 Inorganic Nomenclature I. Cations Cation = when a neutral atom loses electrons they form cations less electrons than a neutral atom makes the atom positive (has more protons than electrons therefore positive) Naming named the same as the parent element Cation formation: Examples: Potassium atom = potassium ion (cation) + 1 electron lost K K + + e - Named for parent therefore called potassium ion Mg Mg e - Named for parent = magnesium ion Al Al e - Named for parent = aluminum ion II. Anions Anion = when a neutral atom gains electrons they form anions Naming take parent name and change ending to ide Anion formation: Examples: Cl + e - Cl - chloride ion (instead of chlorine) O + 2e - O 2- oxide ion N + 3e - N 3- nitride ion Recap = cation named after parent anion 1 st part of parent name with ide ending III. How do you know which does which? Ions usually form when metals combine with nonmetals metals = cations/ nonmetal = usually anion Page 2 of 9

3 3 Chemistry 047 Inorganic Nomenclature Charge of the ion can be predicted from the elements position on the periodic table: Metals: * all metals lose e- to form positive ions On the periodic table: note charge is same as group # Group 1A (all metals) - far left lose 1 e- to form 1 + ions Group 2 A (metals) alkali metals lose 2 e- to form 2 + ions Group 3A (aluminum only predictably) loses 3 e- to form 3 + ions Transition metals: Generally form cations no predictable pattern Nonmetals: *nonmetals form anions (negative charged ions) by gaining electrons Group 5A (15) = 3 - ions N 3-, P 3- Group 6A (16) = 2 - ions O 2-, S 2- Group 7A (17) = 1 - ions F -, Cl -, Br -, I - II. Creating formulas from ions Ionic compound: formed when ions bond The ionic compound must be neutral = have a net charge of 0 If it is ionic charges must add up to zero in the formula A.: the hard way but the explanation why i.e., (Note: these are NOT balanced eqtns!) Na + and Cl - NaCl Na is 1 + and Cl is 1- so is neutral Ca 2+ and F CaF2 Ca has a 2+ charge and F only has 1- so in order to balance you need 2 F s Writing Formula from names of elements: 1. Write formula for metal ion followed by formula for nonmetal 2. Combine the lowest common multiple of cations and anions to make a neutral charge 3. Use subscripts to show number of atoms of each element in compound Page 3 of 9

4 4 Chemistry 047 Inorganic Nomenclature Example: Al 3+ and O 2- Al2O3 (not balanced) long winded explanation: need to find the least common multiple of 3 and 2 so: 2 (3+) and 3 (2-) = 0 End up with: 2 Al 3+ and 3 O 2- so Al2O3 = aluminum oxide B: NOW the easy way!! Criss cross Write the formula for metal (cation) and next to it, the nonmetal (anion) Criss cross charges write as subscripts If charges are equal they cancel each other out Find charges on ion chart i.e., Al 3+ and O 2- criss cross: Al2O3 Mg 2+ and O 2- criss cross but both the same so cancel out still want it to be the least common multiple: MgO Try: Ba 2+ and P 3- criss cross: Ba3P2 III. Naming Inorganic compounds: Naming inorganic molecules can be simple if you have a plan. Either learn the flow chart on the following page or come up with your own plan; but no matter which one you choose, if you remember to stick to your plan you will be able to name inorganic molecules correctly every time. If single ions, follow the instructions given in the previous section. If there are more than 2 elements in the compound, follow the plan below: If starts with an H it s an acid If it is a metal with a non-metal use the ionic system If non-metal and non-metal use the prefix system Page 4 of 9

5 5 Chemistry 047 Inorganic Nomenclature Inorganic nomenclature Suggested naming process H acid metal-nonmetal = ionic system non-metal non-metal = prefix system No O Contains O One charge More than 1 charge prefix (unless 1) anion name cation anion put charge in element name+prefix element -ide end Hydro + ion name(ic) acid name name(ide ending) Roman numeral after cation CCl4 Carbon tetrachloride i.e., hydrochloric acid i.e., Sodium chloride NaCl i.e.,lead (II) iodide ends in ate ends in ite PbI2 -ic acid -ous acid i.e., Sulfuric acid i.e., Sulfurous acid Page 5 of 9

6 6 Chemistry 047 Inorganic Nomenclature Acids: 1. For acids with no Oxygen: Hydrogen combined with one other non-metallic element Sometimes designated as liquid (l) or aqueous (aq) Made when compound is dissolved in water it liberates H + ions 1. Write the prefix hydro followed by the stem of the second element with an ic ending 2. Add the word acid Examples: HF hydrofluoric acid H2S hydrosulfuric acid HCl - hydrochloric acid HBr hydrobromic acid HI hydroiodic acid 2. For acids with Oxygen (=H and polyatomic molecule): Contain hydrogen, oxygen, and one other element (often non-metal but can be metal) = oxyacids 1. Examine compound is it an oxyacid (does formula start with H and contain polyatomic ion with O)? 2. name depends on polyatomic ion ate changes to ic acid ite changes to ous acid Example: H2SO4 (aq) Sulfate = sulfuric acid H2SO3 (aq) sulfite = sulfurous acid HNO3 (aq) nitrate = nitric acid HNO2 (aq) nitrite = nitrous acid Page 6 of 9

7 7 Chemistry 047 Inorganic Nomenclature Ionic system: metal + non-metal 1. Metals that form 1 type of cation i. Name the metal (the cation) first ii. Name the nonmetal (the anion) with the parent stem followed by ide i.e., sodium metal (cation) and chlorine non-metal (anion) write: sodium chloride 2. Metals that form more than 1 type of cation Because many transition metals can form more than 1 type of cation it became confusing, so IUPAC came up with the stock system of naming So when a compound contains a metal that has more than 1 type of cation, the charge on the cation is designated by a Roman numeral in brackets directly following the name of the metal The nonmetal (anion) is treated the same as process 1. above just add the ide ending to the name of the element. 1. Write the name of the cation 2. Follow this with the Roman numeral in brackets for the cation 3. Write the stem of the anion with the ide ending Example: FeCl2 Can figure out charge by doing the reverse criss cross Fe must have a charge of 2+ and Cl must have a charge of So: Iron (II) chloride FeCl3 would be Iron (III) chloride Remember: if it only forms one cation don t use this system A few notes about naming using the ionic system: To name polyatomic compounds that are not acids name cation(s) then identify and use polyatomic anion name Page 7 of 9

8 8 Chemistry 047 Inorganic Nomenclature When naming polyatomic compounds with more than 3 elements it is usually 2 cations with 1 polyatomic anion write the 2 cations first then the polyatomic anion i.e, NaHCO3 sodium hydrogen carbonate Naming hydrates this is when. H2O is at the end of the formula - just add prefix for how many waters are present and the word hydrate to the end of the name: i.e., Ca(NO3)2. 4H2O is Calcium nitrate tetrahydrate, i.e., FeBr3. 6H2O Iron (III) bromide hexahydrate A bit of info on the names of polyatomic ions Many polyatomic ions that contain oxygen are called oxy-anions Have the suffix ate or ite This does not tell you how many oxygens are present, but the ate form contains more oxygens then ite form i.e., sulfate (SO4 2- ) vs sulfite (SO3 2- ) If there are more than 2 types, the one with less then the ite will have the prefix hypo as well as the suffix ite, the one with more than the ate will have prefix per as well as ate i.e., increasing hypo ite ClO - hypochlorite oxygen ite ClO2 - chlorite atoms ate ClO3 - Chlorate per ate ClO4 - perchlorate There are a few strange ones that don t follow ate and ite : Polyatomic Cations (usually polyatomic ions are anions) NH4 + ammonium ion commonly used H3O + hydronium ion Hg2 2+ mercury (I) ion ides that don t follow the ate ite rule Hydroxide OH - Cyanide CN - Peroxide O2 2- Hydrogen sulfide HS - ates Acetate C2H3O2 - Permanganate MnO4 - Page 8 of 9

9 9 Chemistry 047 Inorganic Nomenclature Prefix System: Non-metal + non-metal Compounds formed between 2 nonmetals is a covalent (molecular) compound not an ionic compound Therefore different naming system used 1. When naming compound between 2 nonmetals use this order to determine which element should be named first 1. Si silicon 2. B Boron 3. P phosphate 4. H hydrogen 5. C-carbon 6. S sulfur 7. I Iodine 8. Br bromine 9. N nitrogen 10. Cl chlorine 11. F fluorine 2. Write the name of the first element and if more than 1 atom, use a prefix to indicate amount 3. Write the stem of the second element and add ide and use a prefix to indicate amount (even if one) Note: when oxygen sometimes drop o or a in prefixes to avoid awkward name i.e. monoxide instead of monooxide Prefixes: Mono = 1 Hexa = 6 Di = 2 Hepta = 7 Tri = 3 Octa = 8 Tetra = 4 Nona = 9 Penta = 5 Deca = 10 Examples: CO - carbon monoxide CO2 carbon dioxide PCl3 Phosphorous trichloride SO2 sulfur dioxide P2O5 diphosporous pentoxide CCl4 carbon tetrachloride N2O dinitrogen monoxide N2O4 dinitrogen tetroxide NO nitrogen monoxide S2CL2 disulfur dichloride Page 9 of 9