Add test for zeroth element None in PeriodicTable
Add test for zeroth element None in PeriodicTable

ATenderholt/cclib,langner/cclib,langner/cclib,berquist/cclib,langner/cclib,cclib/cclib,berquist/cclib,cclib/cclib,ATenderholt/cclib,berquist/cclib,cclib/cclib