4. Electron Sharing and      Covalent Bonds  
     Oxygen and Water

The crust of the Earth is 60 % oxygen (atomic percent), in combination with silicon and various third-shell and heavier metals. This is an enormous local enrichment, since the universe as a whole is only 0.05% oxygen. Living organisms are 26% oxygen, mainly in combination with H, C,and N.

  Page 28 of 54 HomeGlossary