Writing Formulas and Naming Compounds PDF

 expression that shows the elements in a compound and the relative proportions of those elements H2O WATER is composed of hydrogen and oxygen in a 2:1 ratio  is a positive or negative integer that is related to the electronic structure of the...

 expression that shows the elements in a compound and the relative proportions of those elements H2O WATER is composed of hydrogen and oxygen in a 2:1 ratio  is a positive or negative integer that is related to the electronic structure of the atom to keep track of the number of valence electrons lost or gained  it is the same charge of an ion  atom that loses e- has the positive charge (+)  atom that gained e- has the negative charge (-) ***Note: For a polyatomic ion, the charge of the ion differs from the oxidation number of the elements that make up the polyatomic ion.  Stock System Old System Name Name *Boldface are more common I. Writing and naming ionic compounds II. Writing and naming covalent compounds A.1. 1) Write the metal (cation) first before followed by the non-metal (anion) 2) Cross-over rule, use the absolute value of the charges (oxidation numbers) of the anion as the subscript for the cation and the absolute value of the cation charge as the subscript for the anion Na1Cl1 NaCl A.2. Mg3(PO4)2 Ca2(SO4)2 CaSO4  A.3.  Hydrates are ionic compounds that absorb water into their solid structures. Anhydrous substances are water free substances. Anhydrous copper (II) sufate, nearly white, absorbs water and turns blue. Copper (II) sulfate that is fully hydrated contains 5 molecules of water. Note dot is used to separate the water molecule. A.4. (NH4)3PO4 + 3- NH4 PO4 B.1. NAMING IONIC COMPOUND a. An ionic compound is named in the order in which the ions appear in the formula. b. The name of the metal (+ion), is given first followed by that of the nonmetal (-ion). c. The cation carry the name of the metal while the name of the anion is derived by changing ending to –ide. LiBr Lithium bromide Na2O Sodium oxide AlI3 Aluminum iodide B.2. NAMING IONIC COMPOUND WHEN METALLIC IONS HAVE VARIABLE OXIDATION NUMBERS  Metals with variable oxidation states maybe named in 2 ways: 1. Old system: The Latin name of the cation with the lower oxidation state is modified to end in –ous, while the cation with the higher oxidation state will end in –ic. 2. Stock System: The English name of the metal is used but the oxidation state is indicated by a Roman numeral enclosed in parentheses Compound Formula Old System Stock System FeCl2 Ferrous chloride Iron (II) chloride Fe2(SO4)3 Ferric sulfate Iron (III) sulfate  Stock System Old System Name Name *Boldface are more common B.2. NAMING IONIC COMPOUND (HYDRATES)  Greek prefixes are used to denote the number of water molecules in the formula. Copper (II) sulfate pentahydrate B.3. Name the first polyatomic ions followed by the second polyatomic ions. (NH4)3PO4 Ammonium phosphate Compounds of Non-metals Non-metal with non-metal 1) The name of the element whose symbol appears first in the formula is written first. The second part of the name is formed by adding suffix –ide to the stem of the second non-metal. Binary acids HCl Hydrogen chloride H2S Hydrogen sulfide  2) If more than one compound is formed by a pair of nonmetals, Greek prefixes are used to indicate the number of atoms of each element present. NO Nitrogen oxide CO Carbon monoxide NO2 Nitrogen dioxide CO2 Carbon dioxide N2O Dinitrogen oxide CO3 Carbon trioxide N2O4 Dinitrogen SO2 Sulfur dioxide tetroxide SO3 Sulfur trioxide   are derived from oxyanions - - ClO4 perchlorate BrO4 perbromate - - ClO3 chlorate BrO3 bromate - - ClO2 chlorite BrO2 bromite - - ClO hypochlorite BrO hypobromite  The name of the oxyacid is derived from the name of the oxyanion with some modification in the suffix. 1. If the name of the oxyanion ends in –ate, the name of the oxyacid will be _______ -ic acid Anion Name of Anion Acid Name of Acid 2- SO4 sulfate H2SO4 sulfuric acid - ClO4 perchlorate HClO4 perchloric acid - BrO3 bromate HBrO3 bromic acid 2. If the name of the oxyanion ends in –ite, the name of oxyacid will be ________-ous acid Anion Name of Anion Acid Name of Acid - ClO2 chlorite HClO2 chlorous acid - NO2 nitrite HNO2 nitrous acid - SO3 sulfite HSO3 sulfurous acid  The prefix per- with the suffic –ic denotes an acid containing one more oxygen atom HClO4 Perchloric acid than the common acid  The suffix –ic denotes the common acid HClO3 Chloric acid  The suffix –ous denotes an acid containing 1 less oxygen atom than the common acid HClO2 Chlorous acid  The prefix hypo- with suffix –ous denotes an acid with 2 less oxygen atoms than the common acid HClO Hypochlorous NON-Ternary:  The prefix hydro- with the suffix –ic denotes HCl Hydrochloric acid an acid with no oxygen  compounds identified by the presence of hydroxide group (OH -)  To name bases, name the metallic portion first, followed by the word hydroxide KOH Potassium hydroxide Fe(OH)2 Ferrous hydroxide or iron (II) hydroxide Fe(OH)3 Ferric hydroxide or iron (III) hydroxide