Valance electrons are defined as the electrons found in the outermost orbital of an atom. These are the electrons that are involved in chemical bonding. Hence, valence electrons determine the reactivity of an element.
Iron is a transition metal (found in the d block of the periodic table). Many of these elements, including iron, have electron configurations in which electrons in their inner shells can also act as valence electrons. These elements can have more than one oxidative state. For example, iron can have a valence of +2 or +3.
The electrons of such metals (such as iron) are called delocalized. Delocalized electrons are not confined to a single atom. This delocalization electrons allow the metals to be great conductors of electricity and thermal energy.