Write the number of atoms of each element found in one unit of the compound:

potassium iodide, ki
sodium sulfide, na2s
silicon dioxide, sio2
carbonic acid, h2co3

The number of atoms of each element found in one unit of the compound:

Potassium iodide, KI, one atom K, one atom I
Sodium sulfide, Na2S, two atoms Na, 1 atom S
Silicon Dioxide, SiO2, one atom Si, two atoms O
Carbonic acid, H2CO3, two atoms H, 3 atoms O