The term 'Abundant Element in Earth's Core' refers to IRON, which is the most abundant element in the Earth's core. IRON is a chemical element with the symbol Fe and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. IRON is by mass the most common element on Earth, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust.