monoatomic dication barium(2+) 137.32700 137.905 BARIUM ION Ba Ba(2+) Ba2+ Barium CAS:22541-12-4 CHEBI:32593 CHEBI:34552 CHEBI:37136 CHEBI:49494 Gmelin:6848 InChI=1S/Ba/q+2 KEGG:C13881 PDBeChem:BA XDFCIPNJCBUZJN-UHFFFAOYSA-N [Ba++] barium(2+) barium(2+) ion barium(II) cation chebi_ontology barium cation divalent metal cation