Formation of the Earth 

Gases thrown out through a supernova cool, and may consequently be incorporated into new stars. The creation of planetary systems might be general in the Universe. Studies propose that the Earth and other planets formed about similar time as the Sun (4.5 billion years ago). When the Sun formed at the center, chemical reactions in the cooler outer areas of the gas concentration generates solid particles that gathered within gravitational forces, first into small bodies termed as planetesimals, and consequently into the planets. In the outer areas of the Solar System temperatures were sufficiently low to create 'ices' of water, solid methane, ammonia and carbon dioxide that are constituents of the giant planets Jupiter and Saturn. The inner planets like Venus, Earth and Mars created at higher

temperatures, and their composition is dominated through elements which create metallic solids, like iron and nickel, and ones along with stable involatile oxides, like SiO₂. Several  other electropositive elements were incorporated like silicates, and a number of also created sulfides and halides. Still the molecular compounds of H, C and N were gaseous at the temperature at which the Earth was created, so that these elements largely escaped, apart from for comparatively small amounts of H₂O,CH₄, CO₂ and NH₃, that were trapped in solid silicates. Noble gas elements (group 18) are uncommon on Earth.

So abundant elements on Earth are ones that were both made efficiently in nuclear reactions in stars, and also created involatile metals or compounds while the Solar System was formed. Consequent heating through radioactive decay allowed the denser metals (Fe, Co and Ni combined with some S) to melt and sink in the direction of the center, forming the core. Silicates and other complex oxides remained like the dominant constituents of the outer layers.