Someone remind me how chemical notation works again...

[KennyR]

Isotope (atomic weight) is superscript, right of the symbol.

Protons in the nucleus is superscript, left of the symbol (not often used).

Number of atoms of the element present is subscript, right of the symbol.

For example, U238 (superscript, damn ascii), is the isotope of Uranium with atomic mass of 238.

[KennyR]

Maybe subscript left is neutrons in the nucleus, but I've almost never seen it used (once you have the atomic mass and the number of protons, you can just subtract and get the neutrons). And neutrons don't have any effect on chemistry.