WRITING AND NAMING CHEMICAL FORMULAS

STANDARDS Predict chemical formulas based on the number of valence electrons and oxidation numbers Name and write the chemical formulas for simple ionic and molecular compounds, including common polyatomic ions. (standard list of common polyatomic ions need to be memorized)

Chemical formula Combination of symbols that represent the composition of a compound. Formula represents –elements involved –ratio of those elements

Structural formula Shows how atoms are joined Shows kind of atoms and the number of atoms used primarily with organic compounds example

Interpreting chemical formulas practice

Monatomic ions Ions formed from a single atom Ion – charged atom –Anion – negative ion –Cation – positive ion oxidation number –Indicates the general distribution of electrons among the bonded atoms

Oxidation numbers periodic table handout - memorize roman numeral –Stock system of nomenclature is used to distinguish the ion charge –Ex. Iron can be +2 or +3 Silver – transition metal but has only +1 – can be named w/o roman number

Older naming system Older naming system – – when metal forms has more than 1 common oxidation number, The ion with the higher charge has a name ending in ic The one with the lower charge has a name ending in ous Ex – Fe+3 – ferric Fe+2 – ferrous

Polyatomic ions A charged group of covalent covalently bonded atoms Handout –Make flash cards

Writing chemical formulas

Naming chemical formulas Handout - memorize chart transition elements

Molecular formula Formulas for compounds that exist as molecules

Empirical formula The simplest formula used to help identify unknown substances Molecular formula of a compound is always written as some whole-number multiple of the empirical formula ionic compounds - always written as empirical formula

Writing empirical formula Practice problems