MAIN ELEMENTS
IN EARTH'S CRUST

(in order of decreasing magnitude)
MAIN ELEMENTS
IN LIVING ORGANISMS
(in order of decreasing magnitude)
O2 O2
Si C
Al H
Fe N
Mg Ca
Ca P
Na K
K (minor) Na
Ti (minor) Cl
Mn (minor) Mg

See the periodic table on page 349 in your book
if you are unfamiliar with the chemical symbols.