A pale-yellow, highly corrosive, poisonous, gaseous halogen element, the most electronegative and most reactive of all the elements, used in a wide variety of industrially important compounds. Atomic number 9; atomic weight 18.9984; freezing point -219.62°C; melting point -223°C; boiling point -188.14°C; specific gravity of liquid 1.108 (at boiling point); valence 1. See Table at element.
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.