Ionic Compound Formulas and Naming for Multivalent Metals Notes

What does multivalent mean?

·  Some transition metals are multivalent

•  This means they have more than one ion form

•  Look at the periodic table (textbook) and locate some multivalent transition metals

•  The most common ion is listed first

•  What is the most common ion for Cu? , Au?

Writing names for multivalent ions

•  We need to distinguish between the two or three different ion forms

•  Use roman numerals from I – VII which corresponds to 1+ - 7+ ion charges

•  For example:

–  Nickel can have two ion forms, Ni2+ and Ni3+

–  These are named nickel (II) and Nickel (III)

Writing formulas for compounds containing a multivalent metal

•  There will only be 1 multivalent metal in a compound

•  It is the metal so it is first in the name (same as ionic compounds)

•  The roman numeral will indicate which ion form is in the compound

***If you are not told what the charge is on the metal with more than one charge, assume it is the most common charge. (charge on top)***

Steps for writing formulas for multivalent compounds

•  Step 1: Identify each ion and its charge

•  Step 2: Determine the total charges needed to balance positive and negative

•  Step 3: Note the ratio of positive ions to negative ions

•  Step 4: Use subscripts to write the formula, 1’s are not shown in subscript

Try the formula for

titanium (IV) fluoride

manganese (III) sulfide

Compound Naming

·  To name metals with more than one charge we use the Stock system.

·  In the Stock system, the charge of the metal is indicated by a Roman numeral written after the name of the metal.

o  Fe2O3 - iron(III) oxide

o  FeO - iron(II) oxide

o  PbO2 - lead(IV) oxide

·  The Stock system should not be used for metals that have only one possible charge.

Steps for Writing names for formulas for compounds that contain a multivalent metal (stock system)

•  Step 1: Identify a multivalent metal

•  Step 2: identify its different ion forms

•  Step 3: determine the ratio of ions in the formula

•  Step 4: what is the charge on the negative ion?

•  Step 5: Balance the positive and negative charges

•  Step 6: Write the name using roman numerals in brackets, following the positive ion to indicate which ion was used

Example: FeI2

Example: PbF4