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 UglyBook: pages 34-42

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 Fe35.4% O27.8% Mg17.0% Si12.6% S2.7% Ni2.7% Ca0.6% Al0.44% All others: 3.5%

Bulk Earth Fe35.4% O27.8% Mg17.0% Si12.6% S2.7% Ni2.7% Ca0.6% Al0.44% All others: 3.5%

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

Reaction potential = E o reaction = E o (reduction) + E o (oxidation) If E o reaction 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) H6.58 He14.17 C3.22 N5.25 Ne10.46 Compare to O: 0.79