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Ch.21 - Transition Elements and Coordination Chemistry
Chapter 21, Problem 82a

Write the formula for each of the following compounds.
(a) Tetraammineplatinum(II) chloride
(b) Sodium hexacyanoferrate(III)

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1
Identify the components of the compound name: ligands, central metal, oxidation state, and counter ions.
For (a) Tetraammineplatinum(II) chloride: Recognize 'tetraammine' indicates four ammonia (NH_3) ligands, 'platinum(II)' indicates Pt with a +2 oxidation state, and 'chloride' indicates Cl^- as the counter ion.
Write the formula for (a) by combining the components: [Pt(NH_3)_4]Cl_2, where the complex ion [Pt(NH_3)_4]^{2+} is balanced by two Cl^- ions.
For (b) Sodium hexacyanoferrate(III): Recognize 'hexacyano' indicates six cyanide (CN^-) ligands, 'ferrate(III)' indicates Fe with a +3 oxidation state, and 'sodium' indicates Na^+ as the counter ion.
Write the formula for (b) by combining the components: Na_3[Fe(CN)_6], where the complex ion [Fe(CN)_6]^{3-} is balanced by three Na^+ ions.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Coordination Compounds

Coordination compounds consist of a central metal atom bonded to surrounding molecules or ions called ligands. The ligands can be neutral or charged and can vary in number and type. Understanding how to identify the central metal and the ligands is crucial for writing the correct chemical formula.
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Oxidation States

The oxidation state of an element in a compound indicates its degree of oxidation or reduction. In coordination compounds, the oxidation state of the central metal is often specified in the name, such as in 'platinum(II)' for tetraammineplatinum(II) chloride. Knowing how to determine and apply oxidation states is essential for accurately representing the compound's formula.
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Nomenclature of Coordination Complexes

The nomenclature of coordination complexes follows specific rules set by IUPAC. The name typically includes the ligands listed in alphabetical order, followed by the metal and its oxidation state in parentheses. Familiarity with these naming conventions is necessary to translate the names of compounds into their correct chemical formulas.
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