By mass, which gas is most common in the compounds that make up the Earth's Crust?
By mass, the most common gas in the compounds that make up the Earth's crust is oxygen (O). Oxygen is a key element in a wide range of minerals and compounds found in the Earth's crust, including silicates and oxides. It combines with other elements to form minerals like quartz, feldspar, and various metal oxides, contributing significantly to the composition of the crust.