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Naming Ionic Compounds Many Ionic compounds contain polyatomic ions: ions made up of more than one atom. Polyatomic ions exist as a unit, so never change the subscript o If you have to balance an ionic compound with a polyatomic ion then ( )and a subscript must be written Ex. Ca (+2) and PO4 (-3) →Ca3(PO4)2 and named Calcium phosphate o Most polyatomic ions are oxyanions Oxyanion is a polyatomic ion composed of an element, usually a nonmetal, bonded to one or more oxygen atoms o If a transitional metal and a polyatomic ion is involved Ex. Cu (+2) and NO3 (-1) →Cu(NO3)2 and named Copper (II) nitrate Note that transitional metals with varying oxidation numbers always have to state which atom was used in the chemical compound whether or not a polyatomic ion is used Rules for naming Ionic Compounds Name the cation (metal) first and the anion (nonmetal) second Monatomic cations use element name Monatomic anions take their name from the root element name plus the suffix –ide o Ex. CsBr is Cesium bromide Determine oxidation numbers of transitional metals compounds before naming to determine Roman number I-IV o Ex. Fe2O3 is Iron (III)oxide Some transitional metals only have one charge Cadmium: Cd+2 Zinc: Zn+2 If the compound has a polyatomic ion, simply name the ion o Ex. NH4Cl is Ammonium chloride If the polyatomic ion has an oxyanions o The ion with more oxygen atoms is named using the root of the nonmetal plus the suffix –ate Ex. NO3- is nitrate Ex. ClO3- is chlorate Ex. CO3-2 is carbonate o The ion with fewer oxygen atoms is named using the root of the nonmetal plus the suffix –ite Ex. NO2- is nitrite o o o o o o The oxyanions with the greatest number of oxygen atoms is named using the prefix per-, the root of the nonmetal, and the suffix-ate ClO4- is perchlorate IO4- is periodate MnO4- is permanganate The oxyanions with one less oxygen atom is named with the nonmetal and the suffix-ate SO4-2 is sulfate The oxyanions with two fewer oxygen atoms is named using the root of the nonmetal plus the suffix –ite Ex. ClO2 – is chlorite The oxyanions with three fewer oxygen atoms is named using the prefix hypo-, the root of the nonmetal, and the suffix –ite Ex. ClO – is hypochlorite Polyatomic ions with 2 transitional metal atoms include a Di-prefix Ex. H2PO4- is Dihydrogen phosphate Ex. Cr2O7-2 is Dichromate Some Hydrogen plus a polyatomic ion are named two ways Ex. HSO4- can be named bisulfate or Hydrogen sulfate Ex. HCO3- can be named bicarbonate or Hydrogen carbonate