Chemical Formation of the Earth

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Chemical Formation of the Earth

• Cloud of elements condenses into planets
• As they do so, they react to form compounds
• They differentiate chemically and by density

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Chemical Makeup of the Earth
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Primary Differentiation of the Earth

• The biggest redox reaction in the world
• metals nonmetals ? compounds
• Focus on metals and nonmetals
• Metal here elements that loses electrons
• Nonmetals here elements that gain electrons

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Chemical Makeup of the Earth

• Bulk Earth
• Fe 35.4
• O 27.8
• Mg 17.0
• Si 12.6
• S 2.7
• Ni 2.7
• Ca 0.6
• Al 0.44
• All others 3.5

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1. So, we end up with excess iron.2. It stays
in the metallic state and is dense, so it sinks
to the center of the earth, forming the metallic
core.3. Next question what other elements go
with Fe to the core? Which do not?
Primary Differentiation of the Earth
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Reaction potential Eoreaction Eo(reduction)
Eo(oxidation) If Eoreaction is positive, the
reaction is favored. If Fe can reduce a cation
of the other element to its neutral state, that
element goes to the core.
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Example Nickel
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Deficient Elements log(cosmic/crust)

• H 6.58
• He 14.17
• C 3.22
• N 5.25
• Ne 10.46
• Compare to O 0.79