gallium Search Term: GalliumSource Category: ASSISTGallium is the chemical element with the symbol Ga. It has the atomic number 31. It is a member of group 13 on the periodic table and is categorised as a post-transition metal. Synonyms: gallium metal; CAS Number: 7440-55-3; Signal Word: Warning. Tags: Gaelement 317440-55-3gallium metal