Naming Inorganic Formulas


Naming formulas means learning to assemble a chemical formula to varify the name. The following examples have a video view of name and and a written explanation.

For source of ions for writing or  naming formulas select either Download Ion Table pdf or Download Ion Table rtf.

Naming Formulas Example One: Lead(II) sulfide versus Lead(IV) sulfide

Name the formula PbS.  In order to name the compound, the ions in it must be identified. By referring to a ion table or typical common cation and anion list, three likely ions can be found: lead(II), lead(IV) and sulfide. They are  Pb+2, Pb+4 and S-2. This allows for two separate lead and sulfur compounds. Namely lead(II) sulfide and lead(IV) sulfide The process can be visualized as follows:

   lead(II) sulfide                 lead(IV) sulfide

   (Cation)x(Anion)y          (Cation)x(Anion)y

   (Pb+2)x(S-2)y                 (Pb+4)x(S-2)y

Cross over the ion charges to produce the subscripts:

   (Pb+2)2(S-2)2                   (Pb+4)2(S-2)4

Reduce the subscripts to the lowest ratio:

   (Pb+2)1(S-2)1                    (Pb+4)1(S-2)2

Remove the charges since the are no longer needed:

   (Pb)1(S)1                             (Pb)1(S)2

Do not show subscripts that are “1":

   (Pb)(S)                                   (Pb)(S)2

Sn and S are not polyatomic not parenthesis are needed

   PbS                                            PbS2

The name for PbS is lead(II) sulfide.


Naming Formulas  Example Two: Chromium(II) borate versus Chromium(III) borate

Name the formula CrBO3.  In order to name the compound, the ions in it must be identified. By referring to a typical common cation and anion list, three likely ions can be found: chromium(II), chromium(III) and boride. They are Cr+2, Cr+3 and BO3-3. This allows for two separate chromium and boride compounds. Namely chromium(II) boride and chromium(III) boride The process can be visualized as follows:

chromium(II) boride       chromium(III) boride

   (Cation)x(Anion)y         (Cation)x(Anion)y

   (Cr+2)x(BO3-3)y           (Cr+3)x(BO3-3)y

Cross over the ion charges to produce the subscripts:

   (Cr+2)3(BO3-3))2           (Cr+3)3(BO3-3)3

Reduce the subscripts to the lowest ratio:

   (Cr+2)3(BO3-3)2             (Cr+3)1(BO3-3)1

Remove the charges since the are no longer needed:

   (Cr)3(BO3)2                       (Cr)1(BO3)1

Do not show subscripts that are “1”:

   (Cr)3(BO3)2                         (Cr)(BO3)

Cr is not polyatomic, parenthesis are not needed. Boride is polyatomic and needs parenthesis, if its sub script out side the parenthesis is “1” or bigger.

   Cr3(BO3)2                              CrBO3

The name for CrBO3 is chromium(II) boride.


   

© Pat Thayer 2014-2016