SECTION 6–3: NAMING COMPOUNDS AND WRITING FORMULAS Physical Science

OBJECTIVES Recognize and describe binary ionic compounds, metals with multiple ions, and polyatomic ions. Name and determine chemical formulas for ionic and molecular compounds.

DESCRIBING IONIC COMPOUNDS Red copper oxide The name of an ionic compound must distinguish the compound from other ionic compounds containing the same elements. The formula of an ionic compound describes the ratio of the ions in the compound. Black copper oxide

BINARY IONIC COMPOUNDS A compound that contains only two elements is called a binary compound. We can easily name an ionic binary compound by using the name of the cation and the name of the ion. If we have a compound that contains sodium and chlorine would be called “sodium chloride.” It doesn’t matter how many atoms of each there are.

BINARY IONIC COMPOUNDS The name for the anion uses part of the name of the nonmetal with the suffix –ide. Remember anion has a negative charge

BINARY IONIC COMPOUNDS Sodium chloride  NaCl Aluminum oxide  Al2O3 Beryllium iodide  BeI2 Magnesium sulfide  Mg2S Calcium nitride  Ca3N2 Boron fluoride  BF3

METALS WITH MULTIPLE IONS Most transition metals have more than one charge. For instance, copper can have a 1+ or a 2+ charge. Iron can have a 2+ or 3+ charge. ALL transition metals will have a positive charge! When we name a compound with a transition metal that has more than one charge, we indicate the charge with a roman numeral: Copper (I) sulfide  Cu2S Copper (II) sulfide  CuS

POLYATOMIC IONS A covalently bonded group of atoms that has a positive or negative charge and acts as a unit is a polyatomic ion. For example, (OH)- is the hydroxide ion. It has a 1- charge.