Definition of "fluorine" [flu•or•ine]

• 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. (noun)

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.

• ""The new mineral does not contain fluorine and is white rather than green, but in all other respects the chemistry matches that for the rock containing kryptonite," Stanley said."
• "It's a corrosive gas, like fluorine, which is used to etch glass."
• "At a red heat platinic fluoride decomposes into metallic platinum and fluorine, which is evolved in the free state."