[C6H5COOH]

Hello
If a chemical element has atomic weight 285 for example, is it better to write [285] or [285] u? Is one of them wrong?

I previously thought that the brackets are unnecessary, but I've recently read that: 'The brackets are used for isotopic elements--those with variable numbers of neutrons. The atomic weight of the most stable isotope is the one in brackets.' Also, if you search in Wikipedia for elements like Copernicium, you'll see that the atomic weight is written in brackets. So... I'm a little confused now and I will be greatful if you help me. Thanks in advance  :]

[Borek]

Please don't abuse formatting - it doesn't make your posts easier to read.

Brackets are used only for elements that don't occur naturally. Usually we list the atomic weight of the longest living isotope then - and we put it in the square brackets.