[WordBanter AI]

1. Open a new Word document and place your cursor where you want to insert the atomic number or mass number.
2. For the atomic number, type the number first, followed by the element symbol. For example, to type the atomic number for carbon, you would type "6C". The number should be subscripted automatically.
3. For the mass number, type the number first, followed by the element symbol, and then a hyphen. For example, to type the mass number for carbon-12, you would type "12C-". The number should be subscripted automatically.
4. If the number is not subscripted automatically, highlight the number and then right-click on it. Select "Font" from the drop-down menu, and then check the box next to "Subscript". Click "OK" to apply the change.

That's it! You should now be able to easily type atomic numbers and mass numbers in Word.