Which Two Atoms Are Most Common in the Earth's Crust?

Oxygen

• Oxygen is the eighth element on the periodic table, and the most common element in the Earth's crust. It comprises 46.6 percent of the crust by weight. Feldspars, which are the most common mineral on Earth, have a chemical formula containing eight oxygen atoms. Quartz, the second most common mineral, is also primarily oxygen by weight.

Silicon

• Silicon, which is element 14 on the periodic table, comprises approximately 27.7 percent of the Earth's crust. Silicates, including quartzes and feldspars, are the most common type of mineral. Feldspars, which make up 60 percent of the crust, contain two or three silicon atoms per molecule. Quartz contains one silicon atom for every two oxygen atoms.

Other Common Elements

• The next most common lithospheric elements are, in descending order, aluminum (8.1 percent), iron (5.0 percent), calcium (3.6 percent), sodium (2.8 percent), potassium (2.6 percent) and magnesium 2.1 percent).

Rare Elements

• Dozens of other elements occur in the Earth's crust, including hydrogen, titanium, gold, silver, thorium, erbium, selenium, mercury and copper. Added together, these elements account for barely 1.5 percent of the lithosphere's total weight.