Silicon, which makes up about 25% of Earth's crust by mass, is used widely in the modern electronics industry. It has three naturally occurring isotopes, ²⁸Si, ²⁹Si, and ³⁰Si. Calculate the atomic mass of silicon. A) 29.2252 amu B) 28.9757 amu C) 28.7260 amu D) 28.0855 amu E) 27.9801 amu

Question

Quizplus · Accepted Answer

To calculate the atomic mass of silicon, we need to take into account the abundance of each isotope and its mass. The given percentages for each isotope are: 
- 28Si: 92.23%
- 29Si: 4.67%
- 30Si: 3.10%

Using these percentages and the respective atomic masses of each isotope (27.9769 amu for 28Si, 28.9765 amu for 29Si, and 29.9738 amu for 30Si), we can calculate the atomic mass of silicon using the formula:

Atomic mass = (% abundance of isotope 1 x atomic mass of isotope 1) + (% abundance of isotope 2 x atomic mass of isotope 2) + (% abundance of isotope 3 x atomic mass of isotope 3)

Substituting the values, we get:

Atomic mass = (0.9223 x 27.9769 amu) + (0.0467 x 28.9765 amu) + (0.0310 x 29.9738 amu)
Atomic mass = 28.0855 amu

Therefore, the atomic mass of silicon is 28.0855 amu, which is closest to choice (D) 28.0855 amu.

Silicon, Which Makes Up About 25% of Earth's Crust by Mass