Using prediction type in the words 'Nuclear Notation' or 'Isotopes' and select it from prediction. This will create a layout structure which will enable users to easily submit Chemical symbols with mass numbers as the superscript and atomic numbers as the subscript. When you are finished creating your isotope, simply click on insert math and it will be added into where you are working. Use the arrow keys on your keyboard to easily maneuver throughout the isotope layout.