CHEM BRAIN

  

Atomic mass of an element is the relative mass of an atom which shows the number of times an atom is heavier than 1/12th of C-12.

  

\( \frac{1}{12}th \times C_{12} = 1 amu \)

simply \( \frac{1}{12} \times 12 = 1amu \)

  

\( avg. \ atomic \  mass = \frac{(m_1 \times a) + (m_2 \times b) + (m_3 \times c)}{a + b + c } \) 

Here m₁ m₂ and m₃ are masses of isotopes and a, b and c are their percentage ratio.