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