Notes: Writing Formulas & Naming Ionic Compounds

Notes:Notes: WritingWriting Formulas & Formulas &

Naming Ionic Naming Ionic CompoundsCompounds

Ionic Ionic CompoCompouundsnds

ionsions - atoms that have a - atoms that have a positive or negative chargepositive or negative charge

Oxidation numberOxidation number – the – the charge that an ion has charge that an ion has from the gain or los of from the gain or los of electronselectrons


Metallic elements tend Metallic elements tend to form ions by losing to form ions by losing one or more electrons, one or more electrons, giving them an overall giving them an overall positive charge. These positive charge. These are called are called cationscations..


Nonmetals tend to form Nonmetals tend to form ions by gaining one or ions by gaining one or more electrons, giving more electrons, giving them an overall negative them an overall negative charge. These are called charge. These are called anionsanions..


An ionic compound is An ionic compound is formed of cations and formed of cations and anions, this means anions, this means they are made from a they are made from a metal and a nonmetal.metal and a nonmetal.


Anions and cations can Anions and cations can also sometimes be made also sometimes be made of groups of elements that of groups of elements that carry an overall charge carry an overall charge called called polyatomic ionspolyatomic ions..


Though made from positively Though made from positively and negatively charged ions, and negatively charged ions, an ionic compound is an ionic compound is electrically neutral.electrically neutral.

The total charge of all the The total charge of all the ions in a compound is ZERO!!!ions in a compound is ZERO!!!

Chemical Chemical FoForrmulasmulas

A chemical formula A chemical formula tells you the type and tells you the type and number of atoms in number of atoms in the representative unit the representative unit of a compound.of a compound.

Writing ChemicWriting Chemicaal l FormulasFormulas

11) Write the symbol for ) Write the symbol for the elements and their the elements and their oxidation number, oxidation number, positive ion first (the positive ion first (the metal).metal).+2


2) Criss cross the 2) Criss cross the numbers and write numbers and write them as subscripts them as subscripts without the signs.without the signs.-1


3) If there is a charge 3) If there is a charge of one, do not write it. of one, do not write it. The one is implied. The one is implied.


4) If you have 4) If you have subscripts that are subscripts that are multiples, reduce multiples, reduce them down.them down.

4 2


5) If using 5) If using polyatomic ions, put polyatomic ions, put parentheses if there parentheses if there are more than one.are more than one.

ExamplesExamples

1.1. Barium & chlorineBarium & chlorine

2.2. Potassium & NitrogenPotassium & Nitrogen

3.3. Lithium & PhosphateLithium & Phosphate

4.4. Iron (III) & NitrateIron (III) & Nitrate

5.5. Manganese (IV) & SulfurManganese (IV) & Sulfur

Naming Ionic Naming Ionic CCompoundsompounds

For naming an ionic For naming an ionic compound,compound,

1) Name the metal.1) Name the metal.2) Name the second element 2) Name the second element

(the non-metal), but change (the non-metal), but change the ending to –ide.the ending to –ide.


If there is a polyatomic If there is a polyatomic ion instead of a single ion instead of a single nonmetal, just name the nonmetal, just name the polyatomic ion, polyatomic ion, don’t don’t change the ending!change the ending!


Example: NaExample: Na22OOSodium oxideSodium oxide

Example: MgClExample: MgCl22

Magnesium chlorideMagnesium chlorideExample NaExample Na22COCO33

Sodium carbonateSodium carbonate


3) If a positive ion (a metal) 3) If a positive ion (a metal) can have more than one can have more than one oxidation number, you have oxidation number, you have to designate its charge in to designate its charge in the name!the name!


We do this by putting the We do this by putting the charge as a Roman numeral charge as a Roman numeral in parenthesis between the in parenthesis between the positive and negative ion. positive and negative ion. Use the reverse criss cross Use the reverse criss cross method to determine what method to determine what goes in parentheses.goes in parentheses.


Example: FeExample: Fe22OO33

Iron (III) oxideIron (III) oxideExample: FeO Example: FeO (remember, oxygen’s (remember, oxygen’s oxidation number is 2-)oxidation number is 2-)

Iron (II) oxideIron (II) oxide


What elements that What elements that don’t need parentheses?don’t need parentheses?

1) Group I, II and IIIA1) Group I, II and IIIA

2) Zn, Cd (always +2) 2) Zn, Cd (always +2)

3) Ag (always +1)3) Ag (always +1)


Which means that Which means that transition metals do transition metals do need parentheses!need parentheses!


Name the negative Name the negative ion and:ion and:

If a nonmetal end in -If a nonmetal end in -ide; if not, end ide; if not, end normally (polyatomic normally (polyatomic ion).ion).

Name these:Name these:

NaNa22S S


NaNa22S sodium sulfideS sodium sulfide



CuClCuCl22



CuClCuCl22 copper (II) copper (II) chloridechloride




KK22SOSO44




KK22SOSO44 potassium potassium sulfatesulfate




KK22SOSO44 potassium sulfate potassium sulfate

Pb(NOPb(NO33))33




KK22SOSO44 potassium sulfate potassium sulfate

Pb(NOPb(NO33))33 lead (III) lead (III) nitratenitrate

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Notes: Writing Formulas & Naming Ionic Compounds