Question

silicon has three naturally occurring isotopes: si - 28 with mass 27.9769 amu and a natural abundance of 92.21%, si - 29 with mass 28.9765 amu and a natural abundance of 4.69%, and si - 30 with mass 29.9737 amu and a natural abundance of 3.10%. calculate the atomic mass of silicon.
express your answer in atomic mass units to four significant figures.

atomic mass of si = amu

Explanation:

Step1: Calculate the contribution of Si - 28

Multiply the mass of Si - 28 by its abundance.
\(27.9769\times\frac{92.21}{100}=27.9769\times0.9221 = 25.8074\)

Step2: Calculate the contribution of Si - 29

Multiply the mass of Si - 29 by its abundance.
\(28.9765\times\frac{4.69}{100}=28.9765\times0.0469 = 1.3590\)

Step3: Calculate the contribution of Si - 30

Multiply the mass of Si - 30 by its abundance.
\(29.9737\times\frac{3.10}{100}=29.9737\times0.0310=0.9292\)

Step4: Sum up the contributions

Add the contributions of the three isotopes.
\(25.8074 + 1.3590+0.9292=28.0956\approx28.10\)

Answer:

\(28.10\) amu