Question

Define and explain atomic mass of an element. 

Answer 1

Atomic mass of an element is the relative mass of its atoms compared with the mass of an single atom of C-12 isotope taken as 12 units. For example, the atomic mass of oxygen is 16 which indicates that an atom of oxygen is 16 times heavier than 1/12th of a ₁₂C atom. 

Atomic Mass Unit (amu) = 1 /12 th the mass of ₁₂C atom.