how to write math or chemistry formula, how to write math or chemistry formula

If all you need to do is super/subscripts, go to Format > Font > Baseline

Check out MathType there is a free 30 day trial for the professional version, if you decide not to purchase it, it will revert to "MathType Lite" which is a essentially the equation editor found in Microsoft Office. It's a pretty good program and works very well. Even with the Lite version you can pretty much do anything you want to do. Works seamlessly with pages.

There area also dedicated Subscript and Superscript ordinals:

Menu > Edit > Special Characters... > Superscripts and Subscripts

eg H₂0

For complex formulae construct them with Grapher, inside the Utilities folder inside the Applications folder, and then Copy/Paste them into Pages.

Peter