1.Sodium is represented as Na while potassium is represented as K. 2.The atomic number of sodium is 11 while that of potassium is 19. 3.The density of sodium is greater than that of potassium. 4.Sodium burns in a Bunsen flame imparting a golden-yellow color while potassium burns with a pale, violet flame. 5.Both react with water producing hydrogen gas, but the reaction of potassium is much more violent as compared to that of sodium.