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Naming/writing Ionic formulas

Naming/writing Ionic formulas. Mr. Shields Regents Chemistry U09 L03. Stock System for Naming Ionic Compounds. We’ve seen how ionic compounds form and what they are. Now Let’s see how we name them … First, There are two ways we can refer to the Oxidation number of an ion

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Naming/writing Ionic formulas

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  1. Naming/writing Ionic formulas Mr. Shields Regents Chemistry U09 L03

  2. Stock System for Naming Ionic Compounds We’ve seen how ionic compounds form and what they are. Now Let’s see how we name them … First, There are two ways we can refer to the Oxidation number of an ion 1)as a superscript such as Fe+2 - Utilized when we write ionic formulas 2)oras a Roman numeral such as Iron (II) - Utilized when writing out the name of the compound Stock System

  3. Naming Ionic Compounds When writing names of ionic compounds we need to be able to differentiate between the various oxidation states 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 to let the reader know which one your referring to, is it … - Iron (II) for Fe+2 or Iron (III) for Fe+3

  4. Naming Ionic Compounds Roman 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 Chloride Not Calcium (II) Chloride. WHY? LOOK at your Reference Table There is only 1 possible oxidation state for these metals

  5. Binary endings Notice the endings for the names of these compounds FeCl3Iron (III) Chloride FeS Iron (II) Sulfide Cu20 Copper (I) Oxide These are binary compounds and the endings for the compound name end in “-ide” by adding it to the stem of the anion - Chlorine becomes “Chloride” - Sulfur becomes “Sulfide” - Oxygen becomes “Oxide”

  6. More than 1 Ox. State Only 1 Ox. State Use Roman numerals No Roman Numerals “-ide” endings

  7. Polyatomic 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 take Several forms: “-ide” , “-ate” or “-ite” Which ending used depends upon which polyatomic is joined to the metal.

  8. Polyatomic Name Endings Name endings can often provide information on How many oxygens are in the polyatomic. For example: ClO2-Chlorite (BrO2- = Bromite) ClO3-Chlorate SO3-2 Sulfite SO4-2Sulfate -ate’s have more Oxygen than -ites NO2- Nitrite NO3- Nitrate

  9. X Writing Chemical Formulas – The Crisscross method 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

  10. 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 PO43- (NH4)3PO4 Smallest whole number ratio

  11. Try These Name the following: CaF2 KClO4 CuO CrCl3 K2SO3 Write the chemical formula for the following: Chromium (II) Nitrate Calcium Acetate Iron (III) oxide Nickel (II) Phosphate Ammonium Hydroxide Calcium Fluoride Potassium Perchlorate Copper (II) oxide Chromium (III) Chloride Potassium Sulfite Cr(NO3)2 Ca(CH3COO)2 Fe2O3 Ni3(PO4)2 NH4OH Note that a Compound Can also be made up of Two polyatomics…

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