98. 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.

Wt Avg Atomic Wt = 28.0577 amu

Explanation:

Atomic Mass = ∑Wt Avg contributions of isotopes of an element

Si-28 => 92.21% => 0.9221 decimal fraction => Wt Avg Si-28 = 0.9221(27.9769) = 25.7695 amu

Si-29 => 4.69% => 0.0469 decimal fraction => Wt Avg Si-29 = 0.0469(28.9765) = 1.3590 amu

Si-30 => 3.10% => 0.0310 decimal fraction => Wt Avg Si-30 = 0.0310(29.9737) = 0.9292

Wt Avg Atomic Wt = ∑Wt Avg Contributions = (25.7695 + 1.3590 + 0.9292)amu = 28.0577 amu

i'm assuming that it's c.) red bank..