Roman numerals are shown after the cation in parenthesis to indicate the oxidation number. Although roman numerals are used to denote the ionic charge of cations it is still common to see and use the endings ous or ic.
Which metals require a roman numeral in the name.
How to name compounds with roman numerals. Roman numerals are used in naming ionic compounds when the metal cation forms more than one ion. Fecl iron i chloride and fecl2 iron. For ionic compounds with transition metals you need to insert a roman numeral after the name of the metal to indicate the transition metal s charge ex.
Naming ionic compounds using ous and ic. Click to see full answer. The old classic or common way of naming names of some ionic compounds.
In our example the transition metal ion fe2 would have the name iron ii. The roman numerals after an ion indicate the charges and therefore help name the compound. The roman numerals in fact show the oxidation number but in simple ionic compounds this will always be the same as the metal s ionic charge.
When we name their compounds we have to specify which oxidation number is involved. These endings are added to the latin name of the element e g stannous stannic for tin to represent the ions with lesser or greater charge respectively. As stated above transition metals require roman numerals when naming the compound they have formed.
There are 38 elements that are called transition metals and they are found in the middle of the periodic table in groups 3 through 12. The metals that form more than one ion are the transition metals although not all of them do this. In naming the transition metal ion add a roman numeral in parenthesis after the name of the transition metal ion.
The roman numeral naming convention has wider appeal because many ions have more than two valences. The roman numeral must have the same value as the charge of the ion. You name ionic compounds with roman numerals according to the format.
To determine what the oxidation number is you must use the anion negative ion to determine what the positive oxidation number is. All metals except al zn and those in groups 1 and 2 can have more than one oxidation number. Likewise people ask how do you use roman numerals when naming compounds.
Some elements have more then one oxidation number and when naming a compound these must be identified. Name of metal oxidation number in parentheses name of anion. Common or trivial names of compounds are sometimes used in informal conversations between chemists especially older chemists.
This variation in charges is the reason that roman numerals are used chemistry.