For example Barium Sulfate is written BaSo4 but why is iron)ii) hydroxide written Fe(OH)2?? Can someone please explain what the bracket does because I am pretty confused right now.
when there are 2 polyatomic ions in one compund you use the brackets
i think it means you multiply, eh i slept through chemistry.
BaSO4 has the subscript 4 on the O because it has 4 O atoms. Fe(OH)2 has two OH's. Not just O, and not just H. Two of the OH group. It could also be written FeO2H2, but the formula Fe(OH)2 provides the extra information that each O and H are paired up in an OH. And there are two of them.
This is part of the convention of writing chemical formulas Take CaSO4 The Ca ion has a 2+ charge. The SO4 ion has a 2- charge. These can combine in 1:1 ratio to give the compound CaSO4. Quite simple - No brackets are required - there can be no confusion that 1 Ca has combined with 1 SO4. However, there are other compounds which are not quite so simple. I will stay with Ca. You want to combine a Ca ion with OH ion(s) to produce the hydroxide You know that Ca has 2+ charge - but the OH ion has a 1- charge. Therefore you require 2 OH ions to combine with the Ca2+ . If you write this as CaOH2 it indicates that the Ca ion is combined with 1 O atom and 2 H atoms. This is not what the compound is. Therefore the compound is written as Ca(OH)2 . This makes it clear that 1 Ca has combined with 2 OH You can go to an extreme case and combine Ca with the phosphate ion , PO4 . The PO4 has a 3- charge and you know that the Ca has a 2+ charge. These can combine as 3Ca ( total 6+charge) and 2 PO4( 6- charge) The complete compound has to be written as Ca3(PO4)2 . The Ca does not require any bracket because there is no confusion about the number of Ca in the compound , but you have to write the 2 PO4 as (PO4)2 to show that 2 complete PO4 have combined with the 3Ca. You cannot write Ca3PO42 This does not make sense - you have to write Ca3(PO4)2
