code: @Override
      public boolean compare(Object object) {
          if (!(object instanceof Element)) {
              return false;
          }
          if (!super.compare(object)) {
              return false;
          }
          Element elem = (Element) object;
          return Objects.equal(atomicNumber, elem.atomicNumber);
      }
docs: Compares an Element with this Element.
  
  @param  object Object of type AtomType
  @return        true if the atom types are equal