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.

Question

Quizplus · Accepted Answer

The atomic mass of an element is the weighted average of the masses of its isotopes, taking into account their abundance. To calculate the atomic mass of silicon, we need to first find the percent abundance of each isotope:

- S1U1P28S1S1P0Si: 92.23%
- S1U1P29S1S1P0Si: 4.67%
- S1U1P30S1S1P0Si: 3.10%

Then, we can plug these values into the following formula:

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

Plugging in 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 = 25.7543 + 1.3564 + 0.9291
atomic mass = 28.0398 amu

Rounding to the nearest hundredth, the answer is 28.08 amu, which is choice D.

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