[reg45]

Most of the mass of the earth is in the core which is composed primarily of nickel and iron. The light stuff, oxygen, silicon, carbon, nitrogen, etc. is found mostly in the crust.

[burzum]

You overestimate the amount of nickel and underestimate the amount of oxygen. From a simple analysis of nuclear fusion in stars the base material of iron and oxygen is obvious. Additionally, while there is certainly a higher concentration of silicates in the crust than in the mantle, the concentration of silicon is still fairly high for the Earth as a whole. The core certainly does have a higher percentage of nickel in the core, but that is only 4%. I don't know what reference you used to get your crazy belief that silicon and oxygen aren't major players in the mantle or that the mass of the core is larger than that of the mantle and crust combined, but as far as the elemental concentrations this is the reference you should use.