Ch 7 Chemical Formulas and Compounds 7 1

Ch. 7: Chemical Formulas and Compounds 7. 1 Chemical Names and Formulas

Chemical Formulas Ø molecular compound l l number of atoms of each element contained in a single molecule of the compound NO 2, CH 2 Cl 2, Ø ionic compound l l ***Contains a metal typically! represents one unit simplest ratio of the compounds anions and cations Mg. O, Mg(OH)2, NH 4 Br

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

Naming Monatomic Ions Ø cations l l l positive 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 Ø anions l l l negative ion written second in formula by element’s root name + ide ending

Binary Ionic Compounds Ø compounds made of two different ions Ø Crossing Over l l 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 Ø combine the names of the two ions

Practice Naming Ø Al and O l l l Ø Al 3+ O 2 Al 2 O 3 aluminum oxide Mg and Br l l l Mg 2+ Br 1 Mg. Br 2 magnesium bromide Ø Cu and Br l l l Cu 2+ Br 1 Cu. Br 2 copper (II) bromide OR Cu 1+ Br 1 Cu. Br copper (I) bromide

Practice Writing Formulas Ø iron (III) sulfide l l Ø Fe 3+ Fe 2 S 3 S 2 - cadmium oxide l l l Ø Cd 2+ O 2 Cd 2 O 2 Cd. O potassium nitride l l Ø K 1+ K 3 N N 3 - tin (IV) sulfide l l l Sn 4+ Sn 2 S 4 Sn. S 2 -

Cmpds with Polyatomic Ions Ø the cation or anion could be a group of covalently bonded atoms instead of one atom Ø most polyatomic ions are oxyanions: l l l polyatomic ions containing oxygen more than one polyatomic anion can exist for one element sulfate ion: SO 42 sulfite ion: SO 32 -

Practice Naming Ø KNO 3 l l potassium nitrate from K 1+ and NO 31 - Ø Cu(OH)2 l l copper (II) hydroxide from Cu 2+ and OH 1 - Ø NH 4 Br l l ammonium bromide from NH 41+ and Br 1 - Ø Ca. SO 4 l l calcium sulfate from Ca 2+ and SO 42 -

Practice Writing Formulas Ø sodium permanganate l l Ø Na 1+ Mn. O 41 Na. Mn. O 4 iron (II) chlorite l l Ø Fe 2+ Cl. O 21 Fe(Cl. O 2)2 ammonium acetate l l Ø NH 41+ CH 3 COO 1 NH 4 CH 3 COO calcium carbonate l l Ca 2+ CO 32 Ca. CO 3