Why does not the atomic mass of an element represemt the actual mass of its atom ?

Explanation

Atoms of different elements are very small in size and their actual mass are extremely small . For example , the mass of an atom of hydrogen is `1.67xx 10 ^(-27)` Kg. To solve this problem , we consider the relative atomic masses of the elements .The relative atomic mass of hydrogen is 1 u and its correspoding gram atomic mass is 1 g .