Which of the following statements explains why two versions of iron hydroxide, Fe(OH)3 and Fe(OH)2, exist? (A) Transition metals have high melting points. (B) Transition metals form colored compounds. (C) Transition metals are magnetic. (D) Transition metals and their compounds make good catalysts. Or (E) transition metals can have more than one ion.
A transition metal is an element whose atoms have an incomplete d subshell or that can give rise to cations with an incomplete d subshell. The transition metals or transition elements can be found in the d block, between group three and group 11, and in the f block, where they are called the inner transition elements.
Most transition metals can form more than one stable oxidation state, while most main group elements tend to have only one stable oxidation state. Transition metal ions can be converted between their different oxidation states by oxidizing or reducing them. For example, Fe2+ can be oxidized to produce Fe3+. Reduction will convert Fe3+ back to Fe2+. We can see here that iron has formed two stable ions. And if we look at the species given in the question, which are Fe(OH)3 and Fe(OH)2, we can work out that as hydroxide ions have a one minus charge, then in Fe(OH)3, they have an overall charge of three minus. So the iron ion must be Fe3+. And for Fe(OH)2, the iron ion must be Fe2+.
So these two versions of iron hydroxide have been able to form as iron, a transition metal, can form two ions. So the answer to the question “Which of the following statements explains why two versions of iron hydroxide, Fe(OH)3 and Fe(OH)2, exist?” is (E). Transition metals can have more than one ion.