• Click on anisotopic button   and refine it (Which will show the actual shape and size of the atom)

• Type 'edit' (A new window come out, which contains all the information of the molecule. e.g. the molecule contain C H O.)

• Click on the smaller atoms and swoop the selected atoms by oxygen>Right -Click>Type>Oxygen (The smaller size of the atoms tell us the actual element are heavier than the one you assumed)

Note:

         Always refine the structure after you have changed something on the molecule.

Some functional keys:

• Press Ctrl+H to hide hydrogen atoms and press it again, to show them. Now press Ctrl+Q to show/hide Q-peaks. Also try F2, F3 and F4.
•  Left-click on two of the Oxygen atoms to highlight it.
• The keyword 'sel' is used very often in OLEX. It always refers to the current selection, ie the highlighted atoms on the screen. Next, Type 'sel $H' - this will select all hydrogen atoms in the structure.

Proceed if oxygen have been added