To calculate the atomic mass of antimony-123, we can use the information provided about the isotopic abundance and atomic mass of antimony-121.
Let's denote the atomic mass of antimony-123 as x.
The atomic mass of antimony-121 is given as 120.9038 u, and its isotopic abundance is 57.30%. This means that 57.30% of the naturally occurring antimony is antimony-121.
The atomic mass of antimony-123 can be calculated using the following equation:
(Atomic mass of antimony-121 * Isotopic abundance of antimony-121) + (Atomic mass of antimony-123 * Isotopic abundance of antimony-123) = Average atomic mass
(120.9038 u * 0.5730) + (x * (1 - 0.5730)) = Average atomic mass
Simplifying the equation:
69.335174 + 0.427 * x = Average atomic mass
Since we are given the atomic mass of antimony-121 as 120.9038 u, we can substitute it into the equation:
69.335174 + 0.427 * x = 120.9038
Now, we can solve for x, the atomic mass of antimony-123:
0.427 * x = 120.9038 - 69.335174
0.427 * x = 51.568626
x = 51.568626 / 0.427
x ≈ 120.861 u
Therefore, the atomic mass of antimony-123 is approximately 120.861 u.