pseudohalogen
/ˌs(j)uːdəʊˈhalədʒ(ə)n/Chemistry
noun
Any of a group of compounds (in some cases hypothetical) which have small molecules built up from atoms of electronegative elements and which closely resemble the halogens in many respects.
Origin
1920s; earliest use found in Chemical Abstracts. From pseudo- + halogen, after German Pseudohalogen.