The heaviest elements settled in the Earth's center.
The Earth on the other hand starts with a core of iron and radioactive materials such as uranium and plutonium, which release energy in the form of heat, through a process known as nuclear fission. It went through a fusion stage - a "liquid-pasty" state - which allowed that, due to gravity, the denser materials sank towards the center, while the lighter ones floated towards the crust, a process called planetary differentiation.
Atoms, Molecules, Cells, Tissues, Organs, Organ system are all building blocks to growing an organism. Hope this helps. :)
Thing you need to get out of school to leave this place
