Chapter 9: Chemical Names and Formulae

 Monatomic ions: ionic compounds contain a positive (metal) ion and a negative nonmetal ion in a proportion such that their charges add up to zero. Examples: Section 1: Naming Ions

Cations:  Cations: metals tend to lose valence electrons and therefore become positively charged.  Group IA:  Group IIA:  Group IIIA:  Cations are the same name as the metal. Example: 9.1 (cont) :

Anions  Nonmetals tend to gain electrons and become negatively charged ions called anions. Examples:  The charge can be determined by subtracting 8 from the group A number.  The name is not the same as the element, it starts with the stem of the element name and ends in –ide. Example: 9.1 (cont)

 Many transition metals (B groups) form more than one cation with different ionic charges determined by the number of electrons lost. Examples:  There are two methods to name these cations: p542  Stock System: the newer preferred method places Roman numerals in parentheses after the name of the element to indicate the charge. Example:  The older, classical system used the root of the element and added different suffixes. Example: 9.1 (cont)

 Polyatomic ions:  Composed of more than one atom  Behaves as a unit like a monatomic ion  Carries a charge  Often ends in –ite or -ate  Examples: see p (cont)

Writing formulae for binary ionic compounds:  Binary Ionic Compounds are composed of 2 elements  First write the symbol of the cation and then the anion  Add subscripts as needed to balance the charges of each.  LCM method  Crisscross or ‘switcheroo’ method (see p 555)  examples 9.2: Naming and Writing Formulae for Ionic Compounds

Naming Binary Ionic Compounds  Confirm that it is an ionic compound (metal or ions present?)  Place the cation name first followed by the anion name  Examples:  If the metallic element has more than one charge, a Roman numeral must be used.  Examples: 9.2 (cont)

What about ionic compounds with polyatomic ions?  Write as you would the formula of a binary compounds using parentheses to indicate more than one polyatomic ion when needed.  Examples:  When naming, you need to identify that there is a polyatomic ion present (use chart on p 546) and then name as you would the binary ionic compounds.  Examples: 9.2 (cont)

Binary Molecular Compounds  composed of 2 elements that are nonmetals and are not ions.  Electrons are shared, so ionic charges are not used in writing them.  Can combine in more than one way.  Examples: 9.3 Naming and Writing Formulae for Molecular Compounds

Naming Binary Molecular Compounds  Write the names of the elements in the order listed in the formula  Use prefixes to indicate the number of each kind of atom (p569). The prefix mono is omitted for the first element.  End the name of the second element with the suffix –ide.  Examples: 9.3 (cont)

Writing Formulae for Binary Molecular Compounds:  Use the prefixes to tell you the subscript of each element in the formula  Write the correct symbols for the 2 elements with the respective subscripts  Examples: 9.3 (cont)

 Naming Compounds: Flow diagram on p 593  Writing Formulae for compounds: p595  9.4: The names of common acids are listed on p 580. Summary for Naming and Writing Formulae

 The Law of Definite Proportions: in samples of any chemical compound, the masses of the elements are always in the same proportion. This follows Dalton’s Theory which stated that if the atoms are in fixed whole-number ratios, then the masses are also fixed.  Example: 9.5 The Laws Governing How Compounds Form

 Law of Multiple Proportions:  Some compounds contain the same elements but have different properties  Whenever the same 2 elements form more than one compound the different masses of one element that combine with the same mass of the other element are in the ration of small whole numbers.  Example:  Calculating Mass Ratios: see p (cont)

NO, NO 2