Question

Ionic compounds are different from molecular compounds. Why is it necessary to include the Roman numeral with the charge of a transition metal in a formula?

a) To indicate the number of atoms in the compound
b) To indicate the valency of the transition metal
c) To distinguish it from non-transition metals
d) It is not necessary for transition metals

Answer 1

Roman numerals are used in naming ionic compounds to indicate the valency of transition metals, which can have multiple positive charges, thereby preventing ambiguity in compound identification.

Step-by-step explanation:

It is necessary to include the Roman numeral with the charge of a transition metal in a formula to indicate the valency of the transition metal. Transition metals can form two or more cations with different charges, and including the charge as a Roman numeral in the compound's name (after the metal's name) prevents ambiguity.


For example, iron can form Fe2+ and Fe3+; without the Roman numerals iron(II) or iron(III), it would be challenging to distinguish between compounds like FeCl2 and FeCl3. Therefore, in the provided list, option b) 'To indicate the valency of the transition metal' is the correct reason for using Roman numerals when naming ionic compounds containing transition metals.