Editing Period 4 element (section)

===Cobalt===
[[File:Kobalt electrolytic and 1cm3 cube.jpg|frameless|left|upright=0.3]]
[[Cobalt]] (Co) is an element in [[group 9 element|group&nbsp;9]]. Cobalt is commonly used in pigments, as many compounds of cobalt are blue in color. Cobalt is also a core component of many magnetic and high-strength alloys. The only stable isotope, [[cobalt-59]], is an important component of [[vitamin B-12]], while [[cobalt-60]] is a component of nuclear fallout and can be dangerous in large enough quantities due to its radioactivity.