What is the name of PbSO4?
This compound contains the SO42− ion, which has a 2- charge.
For charge balance, the positive ion must have a charge of 2+.
Pb? + (2-) = 0 Pb = 2+
Because lead can form two different positive ions, a Roman numeral (II) is used in the name of the compound:
lead(II) sulfate.