I always thought it was Silicon, but people on Yahoo Answers are saying it is Iron.

 

http://uk.answers.yahoo.com/question/index;_ylt=AhQPUhdyTNSpS6rWpQAOqo8gBgx.;_ylv=3?qid=20080815100943AA8LYBA&show=7#profile-info-I9ox45HHaa

 

What is it? (ignore the atmosphere, for which the answer is Nitrogen)

iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%)

 

Most of the Iron is in the core as it's heavy it sinks....

 

The earths crust is just under 50% oxygen....

 

From:

 

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=350422

 

Which is also the ref the wikipedia page uses:

 

http://en.wikipedia.org/wiki/Earth#Chemical_composition

 

 

There's also;

http://en.wikipedia.org/wiki/Abundance_of_elements_on_Earth#Abundance_of_elements_on_Earth

Can we specify whether we're talking absolute numbers (that's mol%) or we're talking by weight (wt%)? Makes quite a difference.

 

How certain are we of the composition of the core of the earth? Wikipedia uses the word "believed" when discussing the composition of the inner core.

Can we specify whether we're talking absolute numbers (that's mol%) or we're talking by weight (wt%)? Makes quite a difference.

 

How certain are we of the composition of the core of the earth? Wikipedia uses the word "believed" when discussing the composition of the inner core.

 

No ones been to the inner core to take samples...

 

And my numbers were by mass I seem to recall.

we haven't sampled the core as klay said so we can't give very accurate results but what we can do is run tests using various alloys to see which have similar characteristics to what we can tell about the core. iron and nickel seems to fit very very well and we can make reasonable estimates of the ratio.