code: def _add_ideal_atomic_weights_(elemental_array):
      
      for a in elemental_array:
          this_atomic_weight = elements_data[a["symbol"]]["atomic_weight"]
          a["weight"] = a["occurances"] * this_atomic_weight
      return elemental_array
docs: Uses elements.json to find the molar mass of the element in question, and then multiplies that by the occurances of the element.
      Adds the "weight" property to each of the dictionaries in elemental_array
  
      :param elemental_array: an array of dictionaries containing information about the elements in the system
      :return: the appended elemental_array