Question

count the atoms! 3fe(oh)₃

Explanation:

Step1: Determine Fe atoms

The coefficient 3 in front of the formula means there are 3 Fe atoms.

Step2: Determine O atoms

Inside the parentheses, the sub - script 3 multiplies the number of O atoms. So there are $3\times3 = 9$ O atoms.

Step3: Determine H atoms

Similarly, for H atoms, with the sub - script 3 inside the parentheses, there are $3\times3=9$ H atoms.

Step4: Calculate total atoms

Add up the number of Fe, O and H atoms: $3 + 9+9=21$ atoms.

Answer:

21