Common Monoatomic Ions Cations Anions Charge Formula Name Charge Formula Name H+ hydrogen H- hydride Li + lithiumF- fluoride +1 Na + sodium -1 Cl - chloride K+ potassium Br - bromide Cs + caesium I- iodide Ag + silver Mg 2+ magnesium O2- oxide Ca 2+ calcium S2- sulfide +2 Sr 2+ strontium -2 Ba 2+ barium Zn 2+ zinc Cd 2+ cadmium 3+ +3 Al aluminium -3 N3- nitride • Ionic Compounds – often a metal + nonmetal – anion (nonmetal), add “ide ” to element name BaCl 2 barium chloride K2O potassium oxide Mg(OH) 2 magnesium hydroxide KNO 3 potassium nitr ate oxoanions often end with ate 1 Some Common Polyatomic Ions Formula NameFormula Name Cations + + ammonium H3O hydronium NH 4 Common Anions - acetate 2- CH 3COO CO 3 carbonate - cyanide 2- CN CrO 4 chromate OH - hydroxide 2- Cr 2O7 dichromate - chlorate 2- ClO 3 O2 peroxide - nitrite SO 2- sulfite NO 2 3 - 2- NO 3 nitrate SO 4 sulfate 3- - permanganate PO 4 phosphate MnO 4 Oxoanions - NO 2 “ite” nitrite e.g. nitrogen forms 2 oxoanions - NO 3 “ate” nitrate • Some elements can form more than 2 oxoanions e.g. chlorine ClO - hypochlorite (“ hypo” – least) - ClO 2 chlorite - order as before ClO 3 chlorate - ClO 4 perchlorate (“per” – most) • Anions with hydrogen (add one positive charge i.e addition of H +) e.g. S 2- + H + HS - hydrogen sulfide 2- + - CO 3 + H HCO 3 hydrogen carbonate OH - hydroxide ion 2 Acids If formula begins with H and the compound is in aqueous solution, it’s normally a binary acid. Add “ hydro………ic acid” to root of the element. e.g. HCl Hydrogen chloride HCl(aq) Hydrochloric acid OXOACIDS (parents of oxoanions) H+ - NO 2 nitrite ion HNO 2 nitrous acid H+ - NO 3 nitrate ion HNO 3 nitric acid Generally “ous” in the parent acid comes from “ite” in the oxoanion and “ic” in the parent acid comes from “ate” in the oxoanion 2H + 2- SO 3 sulfite ion H2SO 3 sulfurous acid + 2- 2H SO 4 sulfate ion H2SO 4 sulfuric acid • Transition metal ionic compounds – indicate charge on metal with Roman numerals - FeCl 2 2 Cl -2 so Fe is +2 iron(II) chloride (ferrous chloride) - FeCl 3 3 Cl -3 so Fe is +3 iron(III) chloride (ferric chloride) 2- Cr 2S3 3 S -6 so Cr is +3 chromium(III) sulfide 3 Hydrates (compounds that contain water molecules): add “hydrate” preceded by prefix indicating the number of water molecules 2+ 2- e.g. CuSO 4 Cu , SO 4 copper(II) sulfate . CuSO 4 5H 2O (5 water molecules, called water of hydration) copper(II) sulfate pentahydrate Numerical Prefixes for Hydrates and Binary Covalent Compounds 1 mono- 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa- 9 nona- 10 deca- ………… often molecular 4 s Molecular compounds ne eli id Gu – nonmetals or nonmetals + metalloids – common names H 2O, NH 3, CH 4 – element further left in periodic table is 1 st – element closest to bottom of group is 1 st – if more than one compound can be formed from the same elements, use prefixes to indicate number of each kind of atom – last element ends in ide Examples: hydrogen iodide HI SO 2 sulfur dioxide NF nitrogen trifluoride 3 N2Cl 4 dinitrogen tetrachloride Sample Problem Naming Binary Ionic Compounds PROBLEM: Name the ionic compound formed from the following pairs of elements: (a) magnesium and nitrogen (b) iodine and cadmium (c) strontium and fluorine (d) sulfur and caesium PLAN: Use the periodic table to decide which element is the metal and which the nonmetal. The metal (cation) is named first and we use the -ide suffix on the nonmetal name root. SOLUTION: (a) magnesium nitride (b) cadmium iodide (c) strontium fluoride (d) caesium sulfide 5 Sample Problem Determining Formulas of Binary Ionic Compounds PROBLEM: Write empirical formula for the compounds named in the previous Sample Problem. PLAN: Compounds are neutral. We find the smallest number of each ion which will produce a neutral formula. Use subscripts to the right of the element symbol. SOLUTION: 2+ 3- 2+ 3- (a) magnesium nitride (a) Mg and N ; three Mg (6+) and two N (6-); Mg 3N2 2+ - 2+ - (b) cadmium iodide (b) Cd and I ; one Cd and two I (2-); CdI 2 (c) strontium fluoride 2+ - 2+ - (c) Sr and F ; one Sr and two F (2-); SrF 2 + 2- + 2- (d) caesium sulfide (d) Cs and S ; two Cs (2+) and one S ; Cs 2S 6.