diatomic
di.atom.ic \.di--*-'ta:m-ik\ aj [ISV] 1: consisting of two atoms : having two atoms in the molecule 2: having two replaceable atoms or radicals
Webster's English Dictionarydi.atom.ic \.di--*-'ta:m-ik\ aj [ISV] 1: consisting of two atoms : having two atoms in the molecule 2: having two replaceable atoms or radicals