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 %

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.

the answer is barium and copper bromide

i believe the answer is three water molecules