Question

why we put brackets in some chemical formulas
yaar I don't understand that if so in chemistry their is so many elements and one is chemical also so in which molecules we have to put brackets?​

Answer 1

Answer:

The reason is that you need to put a bracket around the complex ion to show how many of those whole complex ions there are in the compound.

• Examples: Mg (OH)2 Al2(SO4)3 (NH4)2SO4.

Answer 2

Answer:

Placing a lowercase number after a bracket helps show how many atoms of that particular molecule there are. Using the image you have attached as an example, the lowercase 2 after the OH helps show that there are 2 hydroxide molecules (i.e. 2 oxygen atoms and 2 hydrogen atoms), while there is only one calcium atom.

Also, brackets may be used for ions outside of chemical formulae because if the valency of the ion turns out to be greater than one, and the compound is a radical ion, it might cause confusion. To avoid it, brackets are used :)

Hope this helps!