One of the chlorine group (fluorine, chlorine, bromine, iodine, astatine) of elements; halogens form monobasic acids with hydrogen, and their hydroxides (fluorine forms none) are also monobasic acids. [G. hals, salt, + -gen, producing]
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halo·gen 'hal-ə-jən n any of the five elements fluorine, chlorine, bromine, iodine, and astatine that form part of group VII A of the periodic table and exist in the free state normally as diatomic molecules
ha·log·e·nous ha-'läj-ə-nəs adj
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hal·o·gen (halґə-jən) (haґlə-jən) [halo- + -gen] an element of a closely related chemical family, all of which form similar (saltlike) compounds in combination with sodium and most other metals. The halogens are bromine, chlorine, fluorine, iodine, and astatine.Medical dictionary. 2011.