Naturally occurring silicon consists of three isotopes with the following isotopic masses and abundances. Isotope Isotopic mass (u) Abundance (%) 2828 Si 27.976926532727.9769265327 92.229792.2297 2929 Si 28.9764947228.97649472 4.68324.6832 3030 Si 29.9737702229.97377022 3.08723.0872 Calculate the average atomic mass of naturally occurring silicon to at least four significant figures.

The question is incomplete, the complete question is;

Silicon has three naturally occurring isotopes with thefollowing masses and natural abundances:

Isotope Mass ({\rm amu}) Abundance (%)

{\rm Si}-28 27.9769 92.2

{\rm Si}-29 28.9765 4.67

{\rm Si}-30 29.9737 3.10

Calculate the atomic mass of silicon.

28.09 amu (to four significant figures)

Explanation:

Given that;

Isotope Mass  Abundance (%)

Si-28 27.9769 92.2

Si-29 28.9765 4.67

Si-30 29.9737 3.10

So we now have;

Relative atomic mass of silicon;

(27.9769  ×  0.9218)  +  (28.9765  ×  0.0471)  +  (29.9738  ×  0.0312)

25.789 + 1.365 + 0.9351 = 28.09 amu (to four significant figures)

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