The isotopes are represented with two numbers before the atom symbol. One number means the atomic number (number of protons) and is placed on the left lower corner, the other number is that mass number (number of protons and neutrons) and is placed on the right upper corner. With that, 1) (8, 18) O: 8 is the atomic number and 18 is the mass number; 2) (10, 22) Ne: 10 is the atomic number and 22 is the mass number; 3) (25, 53) Mn: 25 is the atomic number and 53 is the mas number; 4) (11, 24) Na: 11 is the atomic number and 24 is the mass number; (22, 47) Ti: 22 is the atomic number and 47 is the mass number. The two numbers are placed without parentheses, again atomic number on the left lower corner and the mass number on the left upper corner.
