Ch. 7: Chemical Formulas and Compounds 7.1 Chemical Names and Formulas

Chemical Formulas molecular compound ionic compound number of atoms of each element contained in a single molecule of the compound NO2, CH2Cl2, ionic compound ***Contains a metal typically! represents one unit simplest ratio of the compounds anions and cations MgO, Mg(OH)2, NH4Br

Monatomic Ions ions formed from a single atom Not all representative elements easily form ions Some atoms form covalent bonds instead Others form ions without noble gas configurations d and p-block metals many form 2+ or 3+, some +1 or +4

Naming Monatomic Ions cations anions positive ion negative ion written first in formula by element’s name add a Roman Numeral if it can form more than 1 type of ion that is called the STOCK SYSTEM anions negative ion written second in formula by element’s root name + -ide ending

Binary Ionic Compounds compounds made of two different ions Crossing Over write two ion types with correct charges make the anion’s charge, the cation’s subscript make the cation’s charge, the anion’s subscript simplify the ratio if possible combine the names of the two ions

Practice Naming Al and O Mg and Br Cu and Br Al3+ O2- Al2O3 aluminum oxide Mg and Br Mg2+ Br1- MgBr2 magnesium bromide Cu and Br Cu2+ Br1- CuBr2 copper (II) bromide OR Cu1+ Br1- CuBr copper (I) bromide

Practice Writing Formulas iron (III) sulfide Fe3+ S2- Fe2S3 cadmium oxide Cd2+ O2- Cd2O2 CdO potassium nitride K1+ N3- K3N tin (IV) sulfide Sn4+ S2- Sn2S4 SnS2

Cmpds with Polyatomic Ions the cation or anion could be a group of covalently bonded atoms instead of one atom most polyatomic ions are oxyanions: polyatomic ions containing oxygen more than one polyatomic anion can exist for one element sulfate ion: SO42- sulfite ion: SO32-

Practice Naming KNO3 NH4Br Cu(OH)2 CaSO4 potassium nitrate from K1+ and NO31- Cu(OH)2 copper (II) hydroxide from Cu2+ and OH1- NH4Br ammonium bromide from NH41+ and Br1- CaSO4 calcium sulfate from Ca2+ and SO42-

Practice Writing Formulas sodium permanganate Na1+ MnO41- NaMnO4 iron (II) chlorite Fe2+ ClO21- Fe(ClO2)2 ammonium acetate NH41+ CH3COO1- NH4CH3COO calcium carbonate Ca2+ CO32- CaCO3