Calcium hydroxide and why there are parenthesis

Basics but in calcium hydroxide Ca(OH)2 ,
\*Where the 2 is a subscript what do the parenthesis symbolize? Why isnt it just CaOH2?? 




Parenthesis in a chemical formula indicate that the elements inside them form a group. If followed by a sub-scripted number then there are that number of the group attached.


So Ca(OH)2 is different from CaOH2. It has an extra oxygen.


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