Why do chemists use parentheses? Give an examples.

Question

Explain please.

Answer 1

In chemistry, we use parentheses to help identify that there is more than one polyatomic ion present. 

 

Example:  H₂SO₄   means there are 2 H⁺ ions, 1 S^-2 ion, and 4 O^-2 ions. There is only one sulfate ion so no parentheses is needed.

 

However, aluminum sulfate does require parentheses because there is more than one sulfate ion and we want to  make sure we are accounting for the S and O portions. 

 

Correct: Al₂(SO₄)₃           

Incorrect: (Al)₂(SO₄)₃     There is no need to put parentheses around Al because it is a single ion.