2. расставьте индексы в формулах следующих соединений: а) k..o.. i б) аl..i.. v i в) р..cl..

K2O - оксид калия
AlI3 - йодид алюминия
P2Cl5 - хлорид фосфора(V)

a) k2o, potassium oxide.
- The symbol for potassium is K, so the index for potassium is 2.
- The symbol for oxygen is O, so the index for oxygen is 1.
- Writing the formula for potassium oxide, we place the indixes below the elements: K2O.

b) al2o3, aluminum oxide.
- The symbol for aluminum is Al, so the index for aluminum is 2.
- The symbol for oxygen is O, so the index for oxygen is 3.
- Writing the formula for aluminum oxide, we place the indixes below the elements: Al2O3.

c) pcl5, phosphorus pentachloride.
- The symbol for phosphorus is P, so the index for phosphorus is not needed since it is only one atom.
- The symbol for chlorine is Cl, so the index for chlorine is 5.
- Writing the formula for phosphorus pentachloride, we place the indixes below the elements: PCl5.