Editing Period 4 element (section)

===Iron===
[[File:Iron electrolytic and 1cm3 cube.jpg|frameless|left|upright=0.3]]
[[Iron]] (Fe) is an element in [[group 8 element|group&nbsp;8]]. Iron is [[Abundance of elements on Earth|the most common on Earth]] among elements of the period, and probably the most well-known of them. It is the principal component of [[steel]]. [[Iron-56]] has the lowest energy density of any isotope of any element, meaning that it is the most massive element that can be produced in [[supergiant]] [[star]]s. Iron also has some applications in the human body; [[hemoglobin]] is partly iron.