The earth composition is given below by percentage. 1. oxygen, 46.6 percent by weight; 2. silicon, 27.7 percent, 3. aluminum, 8.1 percent, 4. iron, 5 percent, 5. calcium, 3.6 percent, 6. sodium, 2.8 percent, 7. potassium, 2.6 percent, 8. magnesium, 2.1 percent also check what is the composition in air.