why have he brackets around the (OH)2

and not just OH2

it ask to lsit each element and the number of atoms present.

If it was just OH2 then it would be a differnt element, water actually. The brackets are there to indicate that it is together, and to show you there is 2 of each, the 2 just at the end as you put it would indicate only 1 oxygen atom and 2 hydrogen atoms. Because it is a compound it is placed together in brackets.

See my response to Sarah's original question.

I should have said to look at Sam's original post and my response.

The brackets around (OH)2 in a chemical formula are used to indicate that the subscript 2 applies to both the O and H within the brackets. Without the brackets, OH2 would be read as two separate entities, OH and 2, rather than a single molecule together.

To list each element and the number of atoms present in the compound, follow these steps:

1. Write down the chemical formula: (OH)2

2. Identify the elements present in the formula: In this case, there are two elements, oxygen (O) and hydrogen (H).

3. Determine the number of atoms for each element:
- Oxygen (O): Since there is one O within the brackets and the subscript 2 applies to it, there are 1 x 2 = 2 oxygen atoms.
- Hydrogen (H): Likewise, the subscript 2 applies to the H within the brackets, so there are 1 x 2 = 2 hydrogen atoms.

Therefore, the list of elements and the number of atoms present in (OH)2 would be: oxygen (O) - 2 atoms, hydrogen (H) - 2 atoms.