Transcript Chemical Formation of the Earth

Chemical Formation of the Earth
1. Cloud of elements condenses into
planets
2. As they do so, they react to form
compounds
3. They differentiate chemically and by
density
Chemical Makeup of the Earth
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
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%
Primary Differentiation of the Earth
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?
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.
Example: Nickel
Deficient Elements:
log(cosmic/crust)
H
He
C
N
Ne
6.58
14.17
3.22
5.25
10.46
Compare to O: 0.79