63/29 Cu (copper-63) 65/29 Cu (copper-65) 24/12 Mg (magnesium 24) 25/12 Mg (magnesium 25) 26/12 Mg (magnesium 26) 6/3 Li (lithium 6) 7/3 Li (lithium 7)
The top number is the mass number and you find that by adding the number of neutrons and atomic number The bottom number is the atomic number and it’s the number or protons
