<P> The abundance of the chemical elements is a measure of the occurrence of the chemical elements relative to all other elements in a given environment . Abundance is measured in one of three ways: by the mass - fraction (the same as weight fraction); by the mole - fraction (fraction of atoms by numerical count, or sometimes fraction of molecules in gases); or by the volume - fraction . Volume - fraction is a common abundance measure in mixed gases such as planetary atmospheres, and is similar in value to molecular mole - fraction for gas mixtures at relatively low densities and pressures, and ideal gas mixtures . Most abundance values in this article are given as mass - fractions . </P> <P> For example, the abundance of oxygen in pure water can be measured in two ways: the mass fraction is about 89%, because that is the fraction of water's mass which is oxygen . However, the mole - fraction is 33.3333 ...% because only 1 atom of 3 in water, H O, is oxygen . As another example, looking at the mass - fraction abundance of hydrogen and helium in both the Universe as a whole and in the atmospheres of gas - giant planets such as Jupiter, it is 74% for hydrogen and 23--25% for helium; while the (atomic) mole - fraction for hydrogen is 92%, and for helium is 8%, in these environments . Changing the given environment to Jupiter's outer atmosphere, where hydrogen is diatomic while helium is not, changes the molecular mole - fraction (fraction of total gas molecules), as well as the fraction of atmosphere by volume, of hydrogen to about 86%, and of helium to 13% . </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>

99 percent of the earth's atmosphere by mass is made up of only elements. these elements are
find me the text answering this question