chap 3 part 1

Chapter 3 Chemical Compounds 3.1 Ionic and Molecular Compounds - An ionic compound consists of oppositely charged cations anions. Usually the cation is a metal and the anion is a nonmetal or a group of nonmetals. (ie. NaCl) -A molecular compound consists of two or more different nonmetals. It exists as a discrete unit of atoms. (ie. CO2) - NaCl is an ionic compound -CO2 is a molecular compound -O2 is a molecular element 3.2 Monatomic and Polyatomic Ions -In chapter 2 we saw that we can predict charges on some monatomic ions from their positions in the periodic table Polyatomic Ions -A polyatomic ion consists of a group of atoms with an overall net charge. Ionic Compounds with Polyatomic Ions -Many compounds contain a polyatomic anion: CaCO3, calcium carbonate NaHCO3, sodium bicarbonate NaCN, sodium cyanide KNO3, potassium nitrate Naming Polyatomic Ions -the name of the oxoanion ion changes when the number of oxygen atoms bonded to the central atom changes. 3.3 Formulas for Ionic Compounds -An ionic compound has no overall charge, so the charges on the cations and anions must cancel one pure substance, or when it is dissolved. -The formula that shows this ration with the smallest whole number is called its formula unit. Naming Ionic Compounds Containing Metals with Variable Charges -Many metals including most of the transition metals can form more than one type of ion. When these metals are present in ionic compounds, and additional component must be added to the name to distinguish between similar compounds 3.5 Naming and Writing Formulas for Molecular Compounds - Because molecular compounds do not consist of ions, the nonmetals that compose them are in ratios that are difficult to predict