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Mr. Shields Regents Chemistry U09 L03

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Stock System for Naming Ionic Stock System for Naming Ionic CompoundsCompounds

We’ve seen how ionic compounds form and whatthey are.

Now Let’s see how we name them …

First, There are two ways we can refer to theOxidation number of an ion

1) as a superscript such as Fe+2

- Utilized when we write ionic formulas

2) or as a Roman numeral such as Iron (II)- Utilized when writing out the name of the compound

Stock System

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Naming Ionic CompoundsNaming Ionic CompoundsWhen writing names of ionic compounds we need to be able to differentiate between the various oxidationstates of an element.

For example, look at your reference table. What is the possible oxidation states of Iron?

To differentiate between these two you need a way tolet the reader know which one your referring to, is it …

- Iron (II) for Fe+2

or Iron (III) for Fe+3

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Naming Ionic CompoundsNaming Ionic CompoundsRoman numerals are used when writing the name of compounds to specify the oxidation number of the cation

For example: FeCl3 Fe+3 + Cl- Iron (III) Chloride FeS Fe+2 + S-2 Iron (II) Sulfide Cu20 Cu+1 + O2- Copper (I) Oxide

But … AlCl3 is simply Aluminum Chloride, not Aluminum (III) Chloride and CaCl2 is Calcium ChlorideNot Calcium (II) Chloride.

WHY? LOOK at your Reference Table

There is only 1 possible oxidation state for these metals

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Binary endingsBinary endingsNotice the endings for the names of these compounds

FeCl3 Iron (III) ChlorideFeS Iron (II) SulfideCu20 Copper (I) Oxide

These are binary compounds and the endings for the compound name end in “-ide” by adding it to the stemof the anion

- Chlorine becomes “Chloride”- Sulfur becomes “Sulfide”- Oxygen becomes “Oxide”

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More than 1 Ox. StateOnly 1 Ox. State

“-ide” endings

Use Roman numeralsNo Roman Numerals

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Polyatomic Name EndingsPolyatomic Name Endings

Roman numerals are also used when naming Polyatomic ionic compounds

For example:

Cu(NO3)2 Cu+2 + NO3- Copper (II) Nitrate

However, the endings for these polyatomics may takeSeveral forms: “-ide” , “-ate” or “-ite”

Which ending used depends upon which polyatomicis joined to the metal.

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Polyatomic Name EndingsPolyatomic Name EndingsName endings can often provide information onHow many oxygens are in the polyatomic.

For example:

ClO2- Chlorite (BrO2

- = Bromite)ClO3

- Chlorate

SO3-2 Sulfite

SO4-2 Sulfate

NO2- Nitrite

NO3- Nitrate

-ate’s have moreOxygen than -ites

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Writing Chemical Formulas – The Crisscross Writing Chemical Formulas – The Crisscross

methodmethod

The easiest way to determine a chemical formula of an ionic compounds is to use the crisscross method:

1. Determine the oxidation number of each element or polyatomic

2. This number becomes the subscript of the other ion (w/o the charge, i.e. crisscross)

3. An Oxidation number of 1 is not used as a subscript

4. Subscripts must be reduced to the smallest whole number ratio

X

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Crisscross method Crisscross method

Examples of the crisscross method:

Iron (II) Bromide: Fe2+ Br1- FeBr2

Chromium (III) oxide: Cr3+O2- Cr2O3

Calcium sulfide: Ca2+ S2- CaS

Ammonium Phosphate: NH4+1 PO4

3- (NH4)3PO4

Smallest whole number ratio

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Try TheseTry TheseName the following:

CaF2

KClO4

CuOCrCl3K2SO3

Write the chemical formula for the following:

Chromium (II) NitrateCalcium AcetateIron (III) oxideNickel (II) PhosphateAmmonium Hydroxide

Calcium FluoridePotassium PerchlorateCopper (II) oxideChromium (III) ChloridePotassium Sulfite

Cr(NO3)2

Ca(CH3COO)2

Fe2O3

Ni3(PO4)2

NH4OH

Note that a Compound Can alsobe made up ofTwo polyatomics…