What is the average atomic mass of silicon?

The average atomic mass of silicon is approximately 28.0855 atomic mass units (amu). This value is an average of the masses of all naturally occurring isotopes of silicon, taking into account their relative abundances. Silicon has three stable isotopes: silicon-28 (about 92.23% abundance), silicon-29 (about 4.67% abundance), and silicon-30 (about 3.10% abundance). The atomic masses of these isotopes are as follows:

Silicon-28 (28Si): Approximately 27.97693 amu
Silicon-29 (29Si): Approximately 28.97649 amu
Silicon-30 (30Si): Approximately 29.97377 amu
The average atomic mass is calculated using the formula:

Average Atomic Mass = (abundance of isotope 1 × mass of isotope 1) + (abundance of isotope 2 × mass of isotope 2) + (abundance of isotope 3 × mass of isotope 3) + ...

So, for silicon:

Average Atomic Mass = (0.9223 × 27.97693 amu) + (0.0467 × 28.97649 amu) + (0.0310 × 29.97377 amu) ≈ 28.0855 amu

This is the average atomic mass of silicon, and it is commonly rounded to 28.09 amu for simplicity in calculations.