Chapter 9: chemical names and formulas Honors Chemistry Chapter 9: chemical names and formulas

Naming ions Groups 1A, 2A, 3A: form cations, with charges of 1+, 2+, 3+, respectively Groups 5A, 6A, 7A: form anions, with charges of 3-, 2-, 1-, respectively Groups 4A, 8A typically do not form either Ions of transition metals: to be determined by number of electrons lost, typically by calculation based on information from formula unit, such as KMnO4 Identified by appropriate Roman numeral parenthetically added behind name of metal if metal is cation for a given formula unit, such as iron(III) chloride Polyatomic ions: refer to chart on handout; some you will know by virtue of repletion and familiarity

Naming and writing formulas for ionic cpds. Binary compounds: consist of two elements, one metal and one nonmetal Metal name comes first, then anion/nonmetal, as an –ide If transition metal, look for Roman numeral for oxidation state, telling you expected charge for this ion! Think “cris-cross” to solve for correct subscripts Remember that total charge needs to be zero, so total of positives and total of negatives must be equal! Works the same with polyatomic ions, just remember to multiply, as needed, with them as units…and do not distribute subscripts by multiplication!

Naming and writing formulas for molecular compounds Binary compounds: Use prefixes to denote quantities: mono, di, tri, et cetera! Second element is –ide Don’t use mono for first element if it would be the choice

Naming and writing formulas for acids/bases Reality check: acids have hydrogens as cations to dissociate when in aqueous solution, so their formulas must start with H! If the salt of the acid is an –ide, then the acid is hydro-stem-ic acid If the salt is –ite, then the acid is stem-ous acid If the salt is –ate, then the acid is stem-ic acid See page 272 for examples Bases: typically dissociate releasing hydroxide ions in solution Thus: metal hydroxide will by typical name!

Laws governing formulas and names Law of Definite Proportions: atoms in a compound will be in simple whole-number ratios Law of Multiple Proportions: if two compounds are formed from the same elements, they will be in simple whole number ratios; examples that come to mind are CO, CO2

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