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Ionic Compound Formulation & Nomenclature

Ionic Compound Formulation & Nomenclature. 9/15/08. Ionic Compound Formulation & Nomenclature. • All ionic compounds consist of two parts: a cation (a positive ion) and an anion (a negative ion). • Ions are combined in simple, whole-number ratios to balance

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Ionic Compound Formulation & Nomenclature

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  1. Ionic Compound Formulation & Nomenclature 9/15/08

  2. Ionic Compound Formulation & Nomenclature • All ionic compounds consist of two parts: a cation (a positive ion) and an anion (a negative ion). • Ions are combined in simple, whole-number ratios to balance their charges. This results in a net charge of zero, which all ionic compounds MUST have. • The “cross technique” is used to create the correct ratio of ions needed. Example: aluminum (Al+3) and oxygen (O-2). +3-2 +3-2 AlO AlO AlO 2 3 23 1. Write the symbols, then write the charges on each symbol (from green card) 3. Clean up the formula (completely erase all charges) and reduce if necessary. 2. Cross the charges, dropping the + and – symbols (don’t write 1s) So when do you need to reduce?

  3. Ionic Compound Formulation & Nomenclature—con’t. • Here’s two examples of when the ratio needs to be reduced: +2-2 CaO CaO CaO 2 2 +4-2 SnS2 SnS SnS 2 4 2 • some ionic compounds contain polyatomic ions. These ions must be placed in parenthesisfirst before more than one can be shown in a compound. Examples: +3-2 Al (SO4) Al SO4 2 3 +-3 NH4 P (NH4) P 3

  4. Ionic Compound Formulation & Nomenclature—con’t. • Two very important things to remember: 1. Never, ever, EVER add, delete, change, or move a subscript on a polyatomic ion! The only number that “moves” in the cross technique is the charge (which is a superscript). 2. You must use parenthesis on ANY polyatomic ion when you are indicating two or more, even if there is no little subscript on it to remind you to do so! +-3 NH4 P This 4 NEVER moves or changes because it is a subscript. This 1 and 3 can move (be crossed) because they are superscripts. +3- +2- Al OH Fe BrO Al(OH) Fe(BrO) 3 2

  5. Ionic Compound Formulation & Nomenclature—con’t. • Ionic compounds are named with the following rules: • The cation name goes first, the anion name goes second. • cations are usually metals. The name of the cation does not change from the name of the element. • Note: If the element is polyionic (meaning it can have more than one type of charge), this must be indicated by placing a roman numeral after the name to indicate the size of the charge. • anions are either: (1) a single negatively charged element (monatomic)—name of element with ending taken off and “-ide” added. or • (2) a group of elements that carry a negative charge (polyatomic ions = PAIs)—PAIs have their own special names (on green card). Zn+2 = zinc Sc+3 = scandium Fe+2 = iron (II) Fe+3 = iron (III)

  6. Ionic Compound Formulation & Nomenclature—con’t. • Let’s try formulating some compounds (putting them together): Let’s try naming some compounds: • tin (II) permanganate = _______ • barium iodate = _____________ • cobalt (III) hydroxide = _______ • copper (I) thiosulfate = _______ • lithium peroxide = ___________ • magnesium fluoride = ________ • iron (III) bromide = __________ • potassium chlorate = _________ • calcium hypochlorite = _______ • silver nitrate = ______________ • FeO _____________ • Al2O3 _____________ • KCN _____________ • Pb(OH)4 __________ • K2S ______________ • Mn2(SO4)3 ____________ • Na2Cr2O7 _____________ • (NH4)2SO3 ____________ • CsNO3 _______________ • ZnCl2 ________________

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