The provisions of this Charter relative to civil service shall apply to all employees in existing departments of the City now under civil service and all employees in new departments created by City ordinance unless specifically exempted therefrom by Charter, ordinance, state or federal law; Provided; That all elective officers, the heads of all departments, one chief deputy of any department when so provided by ordinance, professional engineers, attorneys, and certified public accountants when employed in their professional capacity, and temporary extra help, shall not be included within the classified civil service.