<span>This question can best be answered using a Periodic Table of Elements. All the elements are listed by their atomic number starting from the top left and moving right and down the table. Starting at element 8, you will find Oxygen with a mass of 15.99 amu, followed by element 9 Fluorine with a mass of 18.99 , element 10 Neon with a mass of 20.18 , element 11 Sodium with a mass of 22.99. Writing them with their symbols you would have; O, F, Ne, Na.</span>
