def _add_ideal_weight_percent_(elemental_array):
    """
    Adds the "weight_percent" 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
    """
    t_mass = _calculate_total_mass_(elemental_array)
    for a in elemental_array:
        a["weight_percent"] = a["weight"] / t_mass * 100
    return elemental_array