What are the reasons/factors that have influenced these levels of development?

because the two particles have an equal charge, the charges will cancel out and give the atom an overall charge of 0. so, if at atom has 35 protons in the nucleus, we could expect it to have 35 electrons orbiting that nucleus.

heat from the core of the earth causes convection currents to occur in the mantle. these currents slowly move the crust around.