What are the three most common elements on earth?

Answer 1

This "answer" does not answer the "question" (which asks about elements, not compounds such as CO2, and has nothing to do with the shape of the Earth's magnetic field!) The fact that an element (such as Oxygen) is "locked away" in compunds (such as oxides) has nothing to do with the abundance of elements -- which was the point of the actual question.

It is correct to say that the answer depends somewhat upon "the chemical composition of the earth[']s core" but there is ample evidence to support the assumption that it is composed primary of iron (plus some nickel), and that leads to the correct answer that Iron is the most common element. Speculations about Titanium are unsupported, and do not add anything relevant to the answer to the question that was asked.

Answer 2

Silicon, Oxygen & Carbon Dioxide

It all depends on the chemical composition of the earths core but it also depends on whether your counting pure elements or compounds. Overall, oxygen is by far the most abundant accounting for almost half of earths mass but very little of this is pure oxygen most of it is locked away in water, oxides and many other compounds because it reacts with so many other elements. If you count pure elements it is likely to be iron, but you just can't be sure until you research the earths inner layers and core! We could have have a core of very little iron and a much larger quantity of an other element like titanium or something. Personally, I think it is very unlikely that the earths core is not composed largely of iron due the shape and size of earths magnetic field.

Iron is the most common element on earth. the size and shape of its' magnetic field is much greater than the size of the earth, this is because it is made of mostly iron. The reason the earth is primarily made of what it is lies in the mass of elements and the distance from the exploding star they can be propelled by that explosion. Most of the Iron that was propelled from the star that created our planet was collected together to form balls of iron combined with other heavier more dense elements, these clusters of highly dense elements eventually began attract the less dense elements in their order of density, the material left over for the moon tended to be the lighter elements like titanium, which is why the Earth's core is not made of titanium.

Answer 3

These elements are (in the Earth crust): Si, Al, O, Ca, Mg, Fe, Na, K, H, C, Ti, P.