Inorganic Compound Naming and Classification

CLASSIFICATION, NAMING AND WRITING FORMULAS OF INORGANIC COMPOUNDS OBJECTIVES: At the end of the lesson, the student is expected to: 1. Recognize and name ionic and covalent compounds 2. Name and write chemical formulas of compounds RECOGNIZING AND NAMING BINARY IONIC COMPOUNDS R...

CLASSIFICATION, NAMING AND WRITING FORMULAS OF INORGANIC COMPOUNDS OBJECTIVES: At the end of the lesson, the student is expected to: 1. Recognize and name ionic and covalent compounds 2. Name and write chemical formulas of compounds RECOGNIZING AND NAMING BINARY IONIC COMPOUNDS RECOGNIZING AND NAMING BINARY IONIC COMPOUNDS  A binary compound is a compound in which only two elements are present.  Examples of binary compounds: NaCl, CO , NH , P O 2 3 4 10  A binary ionic compound is an ionic compound in which one element present is a metal and the other element present is a non-metal. RECOGNIZING AND NAMING BINARY IONIC COMPOUNDS  Binary ionic compounds are named using the following rule: The full name of the metallic element is given first, followed by a separate word containing the stem of the non-metallic element name and the suffix –ide.  Example: NaF  Start with the name of the metal (sodium), follow it with the stem of the name of the non-metal (fluor-), and then add the suffix –ide. The name becomes sodium fluoride.  Names of Selected Common Non-metallic elements Element Stem Name of ion Formula of ion bromine brom- bromide Br - carbon carb- carbide C 4- chlorine chlor- chloride Cl - fluorine fluor- fluoride F - hydrogen hydr- hydride H - iodine iod- iodide I - nitrogen nitr- nitride N 3- oxygen ox- oxide O 2- phosphorus phosph- phosphide P 3- sulfur sulf- sulfide S 2- EXERCISES: Name the following ionic compounds: 1. MgO 2. Al2S3 3. K3N 4. CaCl2 RECOGNIZING AND NAMING BINARY IONIC COMPOUNDS  There are other metals that exhibit a less predictable behavior because they are able to form more than one type of ion.  For example, iron forms both Fe2+ and Fe3+ ions, depending on chemical circumstances.  When naming compounds that contain metals with variable ionic charges, the charge on the metal ion must be incorporated into the name. This is done by using Roman numerals. RECOGNIZING AND NAMING BINARY IONIC COMPOUNDS  For example, the chlorides of Fe2+ and Fe3+ (FeCl and 2 FeCl3, respectively) are named iron (II) chloride and iron (III) chloride.  Likewise, CuO is named as copper (II) oxide. The charge on the non-metal ion present (which does not vary) can be used to calculate the charge on the metal ion if the latter is unknown. RECOGNIZING AND NAMING BINARY IONIC COMPOUNDS  Knowledge about which metals exhibit variable ionic charge and which have a fixed charge is a prerequisite for determining when to use Roman numerals in binary ionic compound names.  Examples of metals that exhibit a fixed-charge behavior are the following: Li+ Na+ K+ Rb+ Cs+ Be2+ Mg2+ Ca2+ Sr2+ Ba2+ Ag+ Zn2+ Cd2+ Al3+ Ga3+ POLYATOMIC IONS  There are two categories of ions: monoatomic and polyatomic. A monoatomic ion is an ion formed from a single atom through loss or gain of electrons. Examples of which are Cl-, Na+, Ca2+, Mg2+, N3- and so on.  A polyatomic ion is an ion formed from a group of atoms (held together by covalent bonds) through loss or gain of electrons.  An example of a polyatomic ion is the sulfate ion, SO -2 4 POLYATOMIC IONS  Polyatomic ions are very stable and general maintain their identity during chemical reactions.  Polyatomic ions are not molecules, they never occur alone as molecules do. Instead, they are always found associated with ions of the opposite charge.  Polyatomic ions are charged pieces of compounds, not compounds themselves. Key element Formula Name of Ion present NO3- Nitrate Formulas NO2- Nitrite and Names Nitrogen NH4+ Ammonium of Some Common N3- Azide Polyatomic SO42- Sulfate Ions HSO4- Hydrogen sulfate or bisulfate Sulfur SO32- Sulfite HSO3- Hydrogen sulfite or bisulfite S2O32- Thiosulfate Phosphorus PO43- Phosphate HPO42- Hydrogen phosphate H2PO4- Dihydrogen phosphate PO33- Phosphite Hydrogen H3O+ Hydronium OH- Hydroxide Key element Formula Name of Ion present ClO4- Perchlorate Formulas ClO3- Chlorate and Names Chlorine ClO2- Chlorite of Some Common ClO- Hypochlorite Polyatomic CO32- Carbonate Ions HCO3- Hydrogen carbonate or Carbon bicarbonate C2O42- Oxalate C2H3O2- Acetate CN- Cyanide MnO4- Permanganate Metals CrO42- Chromate Cr2O72- Dichromate POLYATOMIC IONS 1. Mot of the polyatomic ions have a negative charge, which can vary from -1 to -3. Only two positive ions have been listed: NH4+ (ammonium) and H3O+ (hydronium). 2. Two of the negatively charged polyatomic ions, OH - (hydroxide) and CN- (cyanide), have names ending in –ide, and the rest of them have names ending in either –ate or –ite. POLYATOMIC IONS 3. A number of –ate, -ite pairs of ions, as in SO42- (sulfate) and SO32- (sulfite). The –ate ion always has one more oxygen atom than the –ite ion. Both the –ate and –ite ions of a pair carry the same charge. 4. A number of pairs of ions exist wherein one number of the pair differs from the other by having a hydrogen atom present, as in CO32- (carbonate) and HCO3- (bicarbonate). In such pairs, the charge on the ion that contains hydrogen is always 1 less than that on the other ion. CHEMICAL FORMULAS AND NAMES FOR IONIC COMPOUNDS CONTAINING POLYATOMIC IONS Two conventions not encountered previously in chemical formula writing often arise when writing chemical formulas containing polyatomic ions. 1. When more than one polyatomic ion of a given kind is required in a chemical formula, the polyatomic ion is enclosed in parenthesis, and a subscript, placed outside the parentheses, is use to indicate the number of polyatomic ions needed. An example is Fe(OH)3. CHEMICAL FORMULAS AND NAMES FOR IONIC COMPOUNDS CONTAINING POLYATOMIC IONS 2. So that the identity of polyatomic ions is preserved, the same elemental symbol may be used more than once in a chemical formula. An example formula is the NH4NO3, where the chemical symbol for nitrogen (N) appears in two locations because both the NH4+ and NO3- ions contain N. CHEMICAL FORMULAS AND NAMES FOR IONIC COMPOUNDS CONTAINING POLYATOMIC IONS Examples: Determine the chemical formulas for the ionic compounds that contain these pairs of ions. 1. Na+ and SO42- 2. Mg2+ and NO3- 3. NH4+ and CN- CHEMICAL FORMULAS AND NAMES FOR IONIC COMPOUNDS CONTAINING POLYATOMIC IONS The names of ionic compounds containing polyatomic ions are derived in a manner similar to that for binary ionic compounds. Metal + “stem of the non-metallic name” and the suffix -ide CHEMICAL FORMULAS AND NAMES FOR IONIC COMPOUNDS CONTAINING POLYATOMIC IONS Modification of the naming rule to accommodate polyatomic ion is as follows: 1. If a positive polyatomic ion is present, its name is substituted for that of the metal. 2. If a negative polyatomic ion is present, its name is substituted for that of the non-metal stem name and the “ide” suffix. 3. If both positive and negative polyatomic ions are present, dual name-substitution occurs, and the resulting name includes just the names of the polyatomic ions. CHEMICAL FORMULAS AND NAMES FOR IONIC COMPOUNDS CONTAINING POLYATOMIC IONS Examples: Name the following compounds, which contain one or more polyatomic ions. 1. Ca3(PO4)2 2. Fe2(SO4)3 3. (NH4)2CO3 SUMMARY:  For binary ionic compounds:  Full metal name + Roman numeral if variable-charge metal + stem of non-metal name + suffix -ide  For polyatomic ion-containing compounds:  If (+) ion is polyatomic : Polyatomic ion name + stem of non-metal name + suffix –ide  If (-) ion is polyatomic : Full metal name + Roman numeral if variable charge metal + polyatomic ion name  If both ions are polyatomic : Positive polyatomic ion name + negative polyatomic ion name NAMING BINARY MOLECULAR COMPOUNDS NAMING BINARY MOLECULAR COMPOUNDS A binary molecular compound is a molecular compound in which only two non-metallic elements are present.  Names for binary molecular compounds always contain numerical prefixes that give the number of each type of atom present in addition to the names of the elements present. NAMING BINARY MOLECULAR COMPOUNDS  Rule: The full name of the non-metal of lower electronegativity is given first, followed by a separate word containing the stem of the name of the more electronegative non-metal and the suffix –ide. Numerical prefixes, giving number of atoms, precede the names of both non-metals. NAMING BINARY MOLECULAR COMPOUNDS  Rule: In using the numerical prefixes, the prefix –mono is never used to modify the name of the first element in the compound’s name, but is used to modify the name of the second element in the compound’s name. Exemption: Compounds in which hydrogen is the first listed element in the formula are named without numerical prefixes. Number Numerical Example of Prefix Use Prefix 1 mono- CO Carbon monoxide 2 di- H2F2 Dihydrogen difluoride 3 tri- NCl3 Nitrogen trichloride 4 tetra- S4N4 Tetrasulfur tetranitride 5 penta- ClF5 Chlorine pentafluoride 6 hexa- I2F6 Diiodine hexafluoride 7 hepta- IF7 Iodine heptafluoride 8 octa- P4O8 Tetraphosphorus octoxide 9 nona- P4S9 Tetraphosphorus nonasulfide 10 deca- P4Se10 Tetraphosphorus decaselenide NAMING BINARY MOLECULAR COMPOUNDS Selected Binary Molecular A few binary Compounds that have Common compounds have Names names that are Compound Formula Accepted Common Name completely unrelated H2O Water to the naming rules H2O2 Hydrogen Peroxide just discussed. NH3 Ammonia N2H4 Hydrazine CH4 Methane C2H6 Ethane PH3 Phosphine AsH3 Arsine NOMENCLATURE  According to the IUPAC system (International Union of Pure and Applied Chemistry)  Cations  Monoatomic  Fixed Oxidation State  Variable Oxidation State  Polyatomic  Anions  Monoatomic  Polyatomic NOMENCLATURE  Cations (Monoatomic) I. Fixed Oxidation State – Group I (Potassium - K+) ; Group II (Calcium - Ca2+) – state the name II. Variable Oxidation State a. -ous (lower oxidation state) & -ic (higher oxidation state) system b. Stock system – using Roman numerals (e.g. (I), (II) or (III)) in indicating number of atoms  Cations (Polyatomic) – e.g. NH4+ - ammonium ion NOMENCLATURE  Anions (Monoatomic) – (-ide) Cl - chloride O 2- oxide N 3- nitride S 2- sulfide F- fluoride  Anions (Polyatomic) Oxyanions Partner (-ate [higher], - ite [lower]) ClO- hypo -ite SO42- sulfate ClO2- -ite ClO3- -ate SO 3 2- sulfite ClO4- per -ate EXAMPLES  Name the following compounds: 1. MgBr2 2. CuCl2 3. FeSO4 4. (NH4)3PO3 NAMING COMPOUNDS (ACIDS)  Binary (2 elements are present):  Hydro + root word + -ic acid Examples:  H S – hydrosulfuric acid 2  HCl – hydrochloric acid  H Se – hydroselenic acid 2  HF – hydrofluoric acid NAMING COMPOUNDS (ACIDS)  Polyatomic (3 or more elements are present):  Ends in the following suffixes: -ate ; -ite ; -ic ; -ous acid Oxyacids:  HClO – perchloric acid 4  HClO – chloric acid 3  HClO – chlorous acid 2  HClO - hypochlorous acid  HNO – nitric acid 3  HNO – nitrous acid 2  H PO – phosphorous acid 3 3  H CO – carbonic acid 2 3 NAMING COMPOUNDS (BASES)  M+ and OH- (hydroxide ion)  Examples: 1. NH4OH – ammonium hydroxide (the only non-metal that is combined with OH- 2. Mg(OH)2 – magnesium hydroxide 3. Fe(OH)3 – Iron(III) hydroxide NAMING COMPOUNDS (HYDRATES) Greek prefix Value  Hydrates – salts that can capture mono 1 water molecules di 2  Example: tri 3 tetra 4  CuSO. 5H O – copper sulfate penta 5 4 2 pentahydrate hexa 6  MgSO. 7H O – magnesium hepta 7 4 2 oct 8 sulfate heptahydrate non 9 dec 10  Anhydrous/anhydrates undec 11 dodec 12 WRITING FORMULAS  Sodium hydroxide - Na+ and OH-  Aluminum oxide - Al3+ and OH-  Potassium peroxide - K+ and O2-  Cobaltic phosphate – Co3+ and PO 3- 4  Magnesium hydride - Mg2+ and H-  Mercurous nitrate - Hg 2+ and NO - 2 3 REFERENCES:  Chang, Raymond. General Chemistry, 7th edition, McGraw Hill 2014  Stoker, H. Stephen. Exploring General, Organic and Biological Chemistry, 6th edition. 2013.