Question

Naturally occurring magnesium exists as a mixture of three isotopes. These isotopes are Mg-24 (78.70%, 23.985 u), Mg-25 (10.13%, 24.985 u), and Mg-26 (11.17%, 25.983 u). Calculate the average atomic mass of magnesium.

 

Answer 1

$given \\ m_1= 23.985 u ,\ P_1 = 78.70\% \ (for Mg-24 ) \\ m_2= 24.985 u , \ P_2 =10.13 \% \ (for Mg-25 ) \\ m_3= 25.983u , \ P_3= 11.17 \% \ (for Mg-26)$

average atomic mass of magnesium = $m_1P_1+m_2P_2+m_3P_3$

$=23.985\times0.787+24.985\times0.1013+25.983\times0.1117$

$= 24.3094766 u \ answer$