Naming inorganic compounds begins with naming ions.

• Cations, formed by metal atoms, are named first and have the same name as the metal.
  

• If - and ONLY if - a metal can form different cations, the positive charge is indicated by a Roman numeral in parentheses following the name of the metal.
   
  • Examples:
     
    • Fe⁺² − iron (II)   and   Fe⁺³ − iron (III)
    • Cu⁺¹ − copper (I)   and   Cu⁺² − copper (II)
   
• Roman numerals in parentheses are also used to indicate the oxidation number of a normal anion acting like a cation.
   
  • Example:
     
    • P⁺⁵ − phosphorus (V)