Page 120 - Academic Press Encyclopedia of Physical Science and Technology 3rd InOrganic Chemistry

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Encyclopedia of Physical Science and Technology EN007C-307 July 4, 2001 14:49

Halogen Chemistry

Marianna Anderson Busch
Baylor University

I. The Elements
II. The Hydrogen Halides (Hydrohalic Acids)
III. Other Inorganic Halides
IV. Interhalogen Compounds
V. Halogen Oxides
VI. Oxyacids and Their Anions
VII. Other Inorganic Halogen Compounds
VIII. Astatine
IX. Organic Halogen Compounds

GLOSSARY Hydrogen bonding Attraction of a partially positive hy-
drogen bonded to atom A (generally N, O, or F) in one
Azeotrope Constant-boiling mixture formed during dis- molecule to a partially negative atom B either in the
tillation, when the composition of the vapor phase be- same or another molecule. As the electronegativities
comes identical to the composition of the liquid phase. of atoms A and B increase, the strength of the hydro-
Carbonium ion Positively charged carbon ion that acts gen bonding also increases.
as a Lewis acid or electrophile. Ionic and covalent Adjectives describing the way in
Electron affinity Energy required to remove the most which atoms are held together in a chemical compound.
loosely held electron from an isolated negative ion in Ionicindicatesthattheinteractionbetweenatomsispri-
the gas phase in order to form a neutral atom in the gas marily electrostatic. Covalent indicates that the atoms
phase. More positive electron affinities indicate that the are held together through the sharing of electrons.
electron is more tightly held. Ionization energy or ionization potential Energy re-
Electronegativity Ability of a bonded atom in a molecule quired to remove the most loosely held electron from
to attract electrons to itself. The greater the difference an isolated atom in the gas phase in order to form a
in the electronegativities of two atoms bonded to each positive ion in the gas phase. More positive ionization
other, the greater is the charge separation in the bond. potentials indicate that the electron is more tightly held.
Free radical Species with one or more unpaired elec- Lattice energy Energy released when ions come together
trons. from infinite separation to form one mole of a crystal.

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