Alkali metal halide: Difference between revisions

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Alkali metal halides, or alkali halides, are the family of inorganic compounds with the chemical formula MX, where M is an alkali metal and X is a halogen. These compounds are the often commercially significant sources of these metals and halides. The best known of these compounds is sodium chloride, table salt.^[1]

Halite is the mineral form of sodium chloride.

Structure

Most alkali metal halides crystallize with the face-centered cubic lattices. In this structure both the metals and halides feature octahedral coordination geometry, in which each ion has a coordination number of six. Caesium chloride, bromide, and iodide crystallize in a body-centered cubic lattice that accommodates coordination number of eight for the larger metal cation (and the anion also).^[2]

Ball-and-stick model of the coordination of Cs and Cl in CsCl

Properties

The alkali metal halides exist as colourless crystalline solids, although as finely ground powders appear white. They melt at high temperature, usually several hundred degrees to colorless liquids. Their high melting point reflects their high lattice energies. At still higher temperatures, these liquids evaporate to give gases composed of diatomic molecules.

These compounds dissolve in polar solvents to give ionic solutions that contain highly solvated anions and cations. Alkali halides dissolve large amounts of the corresponding alkali metal: caesium is completely miscible at all temperatures above the melting point.^[3]

The table below provides links to each of the individual articles for these compounds. The numbers beside the compounds show the electronegativity difference between the elements based on the Pauling scale. The higher the number is, the more ionic the solid is.

		Lithium	Sodium	Potassium	Rubidium	Caesium
		Alkali metals
Halogens	Fluorine	LiF (3.0)	NaF (3.1)	KF (3.2)	RbF (3.2)	CsF (3.3)
	Chlorine	LiCl (2.0)	NaCl (2.1)	KCl (2.2)	RbCl (2.2)	CsCl (2.3)
	Bromine	LiBr (1.8)	NaBr (1.9)	KBr (2.0)	RbBr (2.0)	CsBr (2.1)
	Iodine	LiI (1.5)	NaI (1.6)	KI (1.7)	RbI (1.7)	CsI (1.8)

References

^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
^ Huheey, James E.; Keiter, Ellen A.; Kieter, Richard L. (1993). Inorganic chemistry : principles of structure and reactivity (4. ed.). Cambridge, Massachusetts [u.a.]: Harper. pp. 377. ISBN 006042995X.

@@ Line 1: / Line 1: @@
+{{short description|Family of compounds consisting of an alkali metal bonded to a halogen}}
-'''Alkali metal halides''' (also known as '''alkali halides''') are the family of [[inorganic compound]]s with the chemical formula MX, where M is an [[alkali metal]] and X is a [[halogen]]. These compounds are the often commercially significant sources of these metals and halides.  The best known of these compounds is [[sodium chloride]], [[table salt]].<ref>Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.</ref>
-[[File:Halit-Kristalle.jpg|180px|right|thumb|Halite is the mineral form of sodium chloride.]]
+'''Alkali metal halides''', or '''alkali halides''', are the family of [[inorganic compound]]s with the [[chemical formula]] MX, where M is an [[alkali metal]] and X is a [[halogen]]. These compounds are the often commercially significant sources of these metals and halides.  The best known of these compounds is [[sodium chloride]], [[table salt]].<ref>Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. {{ISBN|0-7506-3365-4}}.</ref>
+[[File:Halit-Kristalle.jpg|180px|right|thumb|[[Halite]] is the mineral form of [[sodium chloride]].]]
 ==Structure==
-Most alkali metal halides crystallize with the [[face centered cubic]] lattices. In this structure both the metals and halides feature [[octahedral coordination geometry]], in which each ion has a [[coordination number]] of six.  Caesium chloride, bromide, and iodide crystallize in a [[body-centered cubic]] lattice that accommodates coordination number of eight for the larger metal cation (and the anion also).<ref>Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.</ref>
+Most alkali metal halides crystallize with the [[face-centered cubic]] lattices. In this structure both the metals and halides feature [[octahedral coordination geometry]], in which each ion has a [[coordination number]] of six.  Caesium chloride, bromide, and iodide crystallize in a [[body-centered cubic]] lattice that accommodates coordination number of eight for the larger metal cation (and the anion also).<ref>Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. {{ISBN|0-19-855370-6}}.</ref>
 [[File:NaCl polyhedra.png|180px|left|thumb|Ball-and-stick model of the coordination of Na and Cl in NaCl.  Most alkali metal halides adopt this structure.]]
 [[File:CsCl polyhedra.png|180px|left|thumb|Ball-and-stick model of the coordination of Cs and Cl in CsCl]]
 ==Properties==
 The alkali metal halides exist as colourless [[crystalline]] solids, although as finely ground powders appear white.  They melt at high temperature, usually several hundred degrees to colorless liquids.  Their high melting point reflects their high [[lattice energy|lattice energies]].  At still higher temperatures, these liquids evaporate to give gases composed of diatomic molecules.
+These compounds dissolve in polar solvents to give ionic solutions that contain highly solvated anions and cations. Alkali halides dissolve large amounts of the corresponding alkali metal: caesium is completely miscible at all temperatures above the melting point.<ref name="HKK4">{{cite book|last1=Huheey|first1=James E.|last2=Keiter|first2=Ellen A.|last3=Kieter|first3=Richard L.|title=Inorganic chemistry : principles of structure and reactivity|date=1993|publisher=Harper|location=Cambridge, Massachusetts [u.a.]|isbn=006042995X|pages=[https://archive.org/details/inorganicchemist00huhe_0/page/377 377]|edition=4.|url-access=registration|url=https://archive.org/details/inorganicchemist00huhe_0/page/377}}</ref>
-Melting Point Order:
-BX3<AlX3
+The table below provides links to each of the individual articles for these compounds. The numbers beside the compounds show the electronegativity difference between the elements based on the [[Pauling scale]]. The higher the number is, the more ionic the solid is.
+<!-- more useful would be properties - lattice parameters, melting point, solubility in water, other solvents and molten salts. The focus on electronegativity is something that young chem students adhere to, but is not particularly useful or even interesting in the "adult world"-->
-These compounds dissolve in polar solvents to give ionic solutions that contain highly solvated anions and cations.
+<!-- electronegativity is used by adults, though the others mentioned are, also.  Each is listed in the individual article. -->
+{| class="wikitable" style="text-align:center;margin: 1em auto;"
-The table below provides links to each of the individual articles for these compounds. The numbers beside the compounds show the electronegativity difference between the elements based on the [[Pauling scale]]. The higher the number is, the more ionic the solid is.<!-- more useful would be properties - lattice parameters, m.p., sol in water, the focus on electronegativity is something that young chem students adhere to, but is not particularly useful or even interesting in the "adult world"-->
-<h3><b>Very Important Note:</B><h3><font color="red">All alkali metal hallides are ionic like LiH,CsH,NaH etc...</font>
-<center>
-{| class="wikitable" style="text-align:center"
 |-
 | colspan="2" rowspan="2" | &nbsp;
-! colspan="6" | ''Alkali Metals''
+! colspan="6" | Alkali metals
 |-
 ! [[Lithium]]
@@ Line 30: / Line 30: @@
 ! [[Caesium]]
 |-
-! rowspan="5" | ''H<br>a<br>l<br>o<br>g<br>e<br>n<br>s''
+! rowspan="5" {{verth|va=middle|Halogens}}
 ! [[Fluorine]]
 | [[Lithium fluoride|LiF]] (3.0)  || [[Sodium fluoride|NaF]] (3.1)  || [[Potassium fluoride|KF]] (3.2)
@@ Line 47: / Line 47: @@
 | [[Rubidium iodide|RbI]] (1.7) || [[Caesium iodide|CsI]] (1.8)
 |}
-</center>
 ==References==
@@ Line 53: / Line 52: @@
 ==Further reading==
-*[http://nsrdec.natick.army.mil/LIBRARY/80-89/R81-77.pdf Tastes of the alkali metal halides (except fluorides)]
+*[https://web.archive.org/web/20120512142124/http://nsrdec.natick.army.mil/LIBRARY/80-89/R81-77.pdf Tastes of the alkali metal halides (except fluorides)]
-[[Category:Alkali_metals]]
+[[Category:Alkali metals]]
 [[Category:Halides]]
-[[Category:Metal halides|*]]
+[[Category:Alkali metal halides|*]]
 [[Category:Crystals]]
 [[Category:Salts]]
-{{inorganic-compound-stub}}