What is relative atomic mass of an element ?

The relative atomic mass of an element is defined as the average relative mass of an atom of the element compared with an atom of ¹²₆ C taken as 12 u. Thus, relative atomic mass of an element (A_r) = Average mass of 1 atom of the element / (Mass of one ¹²₆ Can atom/ 12).

The relative atomic mass is denoted by A_r. The relative atomic mass is a pure number, and hence it has been no unit.

The relative atomic mass of an element is heavier than number of times one atom of that element is heavier than 1/12^th of a ¹²₆ C atom. For example, the average relative mass of chlorine is 35.45. This means that an atom of chlorine only average is 35.45/12 times heavier than one atom of ¹²₆ C.

Names, symbols and relative atomic masses of some common are present.