Zinc
Zinc is a transition metal element[1], and has a atomic weight of 65.5[2].
Zinc is considered an essential trace element, deficiency in the element can cause slow growth and healing[3]. It is also used to treat disease such as osteoporosis and wilson's disease[3].
The abundance of zinc in humans is 33000 ppb, which means an average person weighing 70 kilograms would have only 2.31g of zinc[4].