<P> The abundance of chemical elements in the universe is dominated by the large amounts of hydrogen and helium which were produced in the Big Bang . Remaining elements , making up only about 2 % of the universe , were largely produced by supernovae and certain red giant stars . Lithium , beryllium and boron are rare because although they are produced by nuclear fusion , they are then destroyed by other reactions in the stars . The elements from carbon to iron are relatively more common in the universe because of the ease of making them in supernova nucleosynthesis . Elements of higher atomic number than iron ( element 26 ) become progressively more rare in the universe , because they increasingly absorb stellar energy in being produced . Elements with even atomic numbers are generally more common than their neighbors in the periodic table , also due to favorable energetics of formation . </P>
<P> The abundance of chemical elements in the universe is dominated by the large amounts of hydrogen and helium which were produced in the Big Bang . Remaining elements , making up only about 2 % of the universe , were largely produced by supernovae and certain red giant stars . Lithium , beryllium and boron are rare because although they are produced by nuclear fusion , they are then destroyed by other reactions in the stars . The elements from carbon to iron are relatively more common in the universe because of the ease of making them in supernova nucleosynthesis . Elements of higher atomic number than iron ( element 26 ) become progressively more rare in the universe , because they increasingly absorb stellar energy in being produced . Elements with even atomic numbers are generally more common than their neighbors in the periodic table , also due to favorable energetics of formation . </P>
which are the two most abundant chemical elements in the earth 's crust
which are the two most abundant chemical elements in the earth 's crust
hydrogen helium
hydrogen helium