Approximately 100 free elements are found in the earth's crust.
There are eight elements that are found in somewhat of an
abundance. These include: oxygen, silicon, aluminum, iron, calcium,
sodium, potassium, and magnesium.
View page
The abundance of radium in the earth crust is 9.10-10 mg/kg.
View page
The abundance ratio by mass, in the earth's crust, is 1:2305,
approx.