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Hybridization of heavier p block elements[edit]

Hybridization of s and p orbitals to form effective sp hybrid orbitals requires that they have comparable radial extent. While 2p orbitals are on average less than 10% larger than 2s, in part attributable to the lack of a radial node in 2p orbitals, 3p orbitals which have one radial node, exceed the 3s orbitals by 20-33%.[1] The difference in extent of s and p orbitals increases further down a group. The hybridization in of atoms in chemical bonds can be analyzed by considering localized molecular orbitals, for example using natural localized molecular orbitals in a natural bond orbital (NBO) scheme. In methane, CH4, the calculated p/s ratio is approximately 3 consistent with "ideal" sp3 hybridization, whereas for silane, SiH4, the p/s ratio is closer to 2. A similar trend is seen for the other 2p elements. Substitution of fluorine for hydrogen further decreases the p/s ratio.[2]The 2p elements exhibit near ideal hybridization with orthogonal hybrid orbitals. For heavier p block elements this assumption of orthogonality cannot be justified. These deviations from the ideal hybridization were termed hybridization defects by Kutzelnigg.[3]


TY - JOUR T1 - Orthogonal and non-orthogonal hybrids JO - Journal of Molecular Structure: THEOCHEM VL - 169 IS - 0 SP - 403 EP - 419 PY - 1988/8// T2 - AU - Kutzelnigg, W. SN - 0166-1280 DO - http://dx.doi.org/10.1016/0166-1280(88)80273-2 UR - http://www.sciencedirect.com/science/article/pii/0166128088802732 [4]

Kutzelnigg in 1986 highlighted carbon as a unique case which adheres most closely to the  conventional sp hybridization model.

Phosphate Glass Article[edit]

Lede[edit]

Phosphate glasses have been used in lasers (for example Nd doped glass), alkali metal phosphate glasses are sequestration agents for hard water and dispersants for clay processing as well as pigment manufacture. Biocompatible phosphate glases are used in medical applications. Iron phosphate glasses have been investigated for use as hosts for nuclear waste. The phosphate glasses were first investigated by Schott and coworkers in the early part of last century. 20th century by Schott and coworkers. While the glasses have good optical properties such as high transparency to ultraviolet light they were considered to sensitive to moisture to be generally useful. P2O5 was identified by Zachariesen as one of the prototypical network formers in the 1930's.(Take from Brow, Neel and Salih and Neel Pickup reviews) Glasses formed from multiple network formers have been produced, for example aluminophosphate, silicophosphate as well as molybdophosphate and tungstophosphate glasses formed with molybdenum and tungsten oxide [5]

Structure[edit]

Phosphate glasses are based on phosphorus pentoxide, P2O5 as the "network former". Tetrahedral {PO4} units are lnked together by bridging oxygen units. This linking of tetrahedral units is shared with the silicate glasses, which are based on silica as the network former. A structural difference between silicates and phosphates is that while silicates can share all four corners in phosphates a maximum of three corners can be shared.Cite error: A <ref> tag is missing the closing </ref> (see the help page). . Crystalline compounds can be prepared as well as amorphous glasses. Phosphate compounds can be classified by their P/O ratio as follows:

Group Ultraphosphate Metaphosphate Polyphosphate Pyrophosphate Phosphate
O/P <3 3 3.5 4
Qi Q2 and Q3 Q2 Q2 and Q1 Q1 Q0
Example compounds Q2 and Q3 Q2 Q2 and Q1 Q1 Q0
Anions generally polymeric with a cage anion ??? known rings and infinite chains chains discrete O3P-O-PO3 discrete PO4
Glasses Q2 and Q3 Q2 Q2 and Q1 Q1 Q0

Binary, Ternary, Quaternary glasses[edit]

Simple binary glasess derived from from P2O5 and a metal single metal oxide, e.g. Na2O, CaO. Ternary has two defferent metal oxides and quaternary 3. The addition of other oxides allows modificaion of the properties of the glasses.

Preparation of glasses[edit]

Melt quenching- could use P2O5 but too volatile and readily hydrolysed- use a phosphate compound e.g. metaphosphate and a metal carbonate rather than oxide- metaphosphate and carbonate decompose releasing H2O and CO2 respectively which is useful as it aids in homogenizing the melt. .[6]

Sol-gel methods - allow for unusual oxides such as TiO2 to be incorporated. Alkoxides and ???? form sol- wait for gel- calcine to dehydrate.

Mechanism of glass formation[edit]

Add ing oxide to P2O5 causes depolymerization. Van wazer suggested that 2Q2 <-> Q3 +Q1 and 2Q1<-> Q2 + Q0m [7]

Invert glasses[edit]

These are called because there have a high P/O ratio - contain small anionic units and properties depend on nature of the cations present.

Polyphosphate glasses[edit]

Anionic chains of Q2 terahedra terminated by Q1 - metaphosphate with a pyro end-- synthon?? perhaps??

Metaphosphate glasses[edit]

First Graham's salt, formed when NaH2PO4 is heated- consists of chains -commercially known as Calgon, an ion exchange water softener.[8] The composition of metaphosphate glasses approximates to M2O.P2O5, (M is a group 1 alkali metal e.g. sodium) [9] Consists almst entirely of Q2 units. Effect of replacing alkali metal oxide with alkline earth metal (eg. substitute MgO for Na2O ) is to increase the durability of the glass.

Ultraphosphate glasses[edit]

Sensitive to moisture - like P2O5 - some need to nbe kept in sealed ampoules.

Ternary phosphate glasses[edit]

Na2O/CaO/P2O5 glasses much studied as biologically compatible.

=[edit]

Ultraphosphates (Article)[edit]

Ultraphosphates are a group of phosphorus oxyanions that contain a higher proportion of phosphorus than metaphosphates.[10] Lanthanide ultraphosphates, LnP5O14 have optical properties that may have industrial applications [11] Ultraphosphates in common with other condensed phosphates (metaphosphates and polyphosphates) are made up of corner sharing {PO4} units. Where ultraphosphates differ is that they contain {PO4} units that share three corners.[10] The number of shared corners in the {PO4} tetrahedra is sometimes designated as Qi where i is the number of corners shared.[12] P2O5 contains only Q3 units in all of its forms (molecular P4O10 and polymeric). Ultraphosphate compounds contain both Q3 and Q2 units, whereas metaphosphate compounds contain only Q2.

Group Ultraphosphate Metaphosphate Polyphosphate Pyrophosphate Phosphate
O/P <3 3 3.5 4
Q2 and Q3 Q2 Q2 and Q1 Q1 Q0

References[edit]

  • Brow 2000
TY - JOUR
T1 - Review: the structure of simple phosphate glasses
JO - Journal of Non-Crystalline Solids
VL - 263–264
IS - 0
SP - 1
EP - 28
PY - 2000/3/1/
T2 -
AU - Brow, Richard K
SN - 0022-3093
DO - http://dx.doi.org/10.1016/S0022-3093(99)00620-1
UR - http://www.sciencedirect.com/science/article/pii/S0022309399006201
  • Neel Salih 2011
TY - CHAP
AU - Abou Neel, E.A.
AU - Salih, V.
AU - Knowles, J.C.
T1 - 1.117 - Phosphate-Based Glasses
A2 - Ducheyne, Paul
BT - Comprehensive Biomaterials
PB - Elsevier
CY - Oxford
PY - 2011///
SP - 285
EP - 297
SN - 978-0-08-055294-1
DO - http://dx.doi.org/10.1016/B978-0-08-055294-1.00249-X
UR - http://www.sciencedirect.com/science/article/pii/B978008055294100249X



  1. ^ Kaupp, Martin (2007). "The role of radial nodes of atomic orbitals for chemical bonding and the periodic table". Journal of Computational Chemistry. 28 (1): 320–325. doi:10.1002/jcc.20522. ISSN 0192-8651. 
  2. ^ Kaupp, Martin (2014) [1st. Pub. 2014]. "Chapter 1: Chemical bonding of main group elements". In Frenking, Gernod & Shaik, Sason. The Chemical Bond. Wiley-VCH. ISBN 978-1-234-56789-7. 
  3. ^ Kutzelnigg, W. (August 1988). "Orthogonal and non-orthogonal hybrids". 169: 403–419. doi:10.1016/j.ccr.2010.04.011.  Text " Journal of Molecular Structure: THEOCHEM" ignored (help)  – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  4. ^ Kutzelnigg, W. (August 1988). "Orthogonal and non-orthogonal hybrids". 169: 403–419. doi:10.1016/j.ccr.2010.04.011.  Text " Journal of Molecular Structure: THEOCHEM" ignored (help)  – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  5. ^ Rao, chapter 12 oxide glasses Elsevier
  6. ^  ?? Neel Salih
  7. ^ Neel and Salih
  8. ^ Wiberg
  9. ^ Neel Salih
  10. ^ a b J.P. Attfield, Phosphates, In Encyclopedia of Materials: Science and Technology (Second Edition), edited by K.H. Jürgen Buschow Robert W. CahnMerton C. Flemings Bernhard Ilschner Edward J. Kramer Subhash Mahajan Patrick Veyssière, Elsevier, Oxford, 2001, Pages 6896-6901, ISBN 9780080431529, http://dx.doi.org/10.1016/B0-08-043152-6/01222-5. (http://www.sciencedirect.com/science/article/pii/B0080431526012225)
  11. ^ Marie-Thérèse Averbuch-Pouchot, A. Durif Topics in Phosphate Chemistry World Scientific, 1 Jan 1996, 981-02-2634-9
  12. ^ Bioactive functional materials: a perspective on phosphate-based glasses, Abou Neel, Ensanya A., Pickup, David M., Valappil, Sabeel P., Newport, Robert J., Knowles, Jonathan C., 2009,Journal of Materials Chemistry, 19, 6, pages 690 - 701, 10.1039/B810675D, ISSN=0959-9428, url http://pubs.rsc.org/en/content/articlelanding/2009/jm/b810675d#!divAbstract




Marie-Thérèse Averbuch-Pouchot, A. Durif Topics in Phosphate Chemistry World Scientific, 1 Jan 1996, 981-02-2634-9

D Corbridge, CHAPTER 3 - Phosphates, Studies in Inorganic Chemistry, Elsevier, 1995, Volume 20, Pages 169-305, ISSN 0169-3158, ISBN 9780444893079, http://dx.doi.org/10.1016/B978-0-444-89307-9.50008-8. (http://www.sciencedirect.com/science/article/pii/B9780444893079500088)

J.M. Cole, M.R. Lees, J.A.K. Howard, R.J. Newport, G.A. Saunders, E. Schönherr, Crystal Structures and Magnetic Properties of Rare-Earth Ultraphosphates, RP5O14 (R=La, Nd, Sm, Eu, Gd), Journal of Solid State Chemistry, Volume 150, Issue 2, March 2000, Pages 377-382, ISSN 0022-4596, http://dx.doi.org/10.1006/jssc.1999.8610. (http://www.sciencedirect.com/science/article/pii/S0022459699986103)

Bioactive functional materials: a perspective on phosphate-based glasses, Abou Neel, Ensanya A., Pickup, David M., Valappil, Sabeel P., Newport, Robert J., Knowles, Jonathan C., 2009,Journal of Materials Chemistry, 19, 6, pages 690 - 701, 10.1039/B810675D, ISSN=0959-9428, url http://pubs.rsc.org/en/content/articlelanding/2009/jm/b810675d#!divAbstract


J.P. Attfield, Phosphates, In Encyclopedia of Materials: Science and Technology (Second Edition), edited by K.H. Jürgen BuschowRobert W. CahnMerton C. FlemingsBernhard IlschnerEdward J. KramerSubhash MahajanPatrick Veyssière, Elsevier, Oxford, 2001, Pages 6896-6901, ISBN 9780080431529, http://dx.doi.org/10.1016/B0-08-043152-6/01222-5. (http://www.sciencedirect.com/science/article/pii/B0080431526012225)

Examples of ultraphosphates[edit]

Compounds are known that contain anions with the general formulae of (P2O5.(PO3)n)n– where n = 2 - 6, P4O112–, P5O143–, P6O174–, P7O205– and P8O236–. The stoichiometry of the anion is no guide to the structure. For example in the lanthaide ultraphosphates, LnP5O14, the phosphate anionic framework adopts a number of different forms. In Na3Fe8O23 the anion 8O236– has a cage "molecular" structure.



P5O143– P6O174- P7O205– P8O236-




In the classification of phosphates as salts of acids with the formula mH2O.nP2O5 ultraphosphates have m/n < 1, and richer in P2O5 than the metaphosphates ,which are salts of hypothetical acids formulated as H2O.P2O5 with anions PnO3nn–.


Classification of salts Ultraphosphate Metaphosphate Polyphosphate Pyrophosphate Phosphate
Acid H2O:P2O5 Example 2H2O:P2O5 3H2O:P2O5
(m/n) (m/n) <1 (m/n) = 1 1 < (m/n) < 2 (m/n) = 2 (m/n) =3
NdP5O14 Example Example Example Example

An ultraphosphate is a phosphate that is richer in phosphorus pentoxide than the metaphosphates. Examples of some known ultraphosphates showing the proportions of phosphorus pentoxide along with metaphosphate as a comaparison.

Formula of the hypothetical acid Proportions of H2O and P2O5 Examples
Ultraphosphate H2P4O11 H2O.2P2O5
1:2
CuP4O11[1] FeP4O11 ZnP4O11 CdP4O11[2]
H3P5O14 3H2O.5P2O5
1:1.67
??
H4P6O17 2H2O.3P2O5
1:1.5
??
H5P7O20 5H2O.7P2O5
1:1.4
??
Metaphosphate H3PO3 H2O:P2O5
1:1


Some known ultraphosphates include [3]

blah blah [4]

[5]

  1. ^ DOI: 10.1002/zaac.19966221107
  2. ^ 10.1016/S0992-4361(98)80026-X
  3. ^ Corbridge, D. (1995). "Chapter 3: Phosphates". Studies in inorganic Chemistry vol. 20. Elsevier Science B.V. pp. 169–305. ISBN 0-444-89307-5. Retrieved January 30, 2015.  – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  4. ^ Ishida, Seiko; McCormick, Frank; Smith-McCune, Karen; Hanahan, Douglas (15 June 2010). "Enhancing Tumor-Specific Uptake of the Anticancer Drug Cisplatin with a Copper Chelator". Cancer Cell. 17 (6): 574–583. doi:10.1016/j.ccr.2010.04.011.   – via ScienceDirect (Subscription may be required or content may be available in libraries.)
  5. ^ Kumada N.,Kinomura N.,Sleight A.W. (November 2000). "Neutron powder diffraction refinement of ilmenite-type bismuth oxides: ABiO3 (A = Na, Ag)". Materials Research Bulletin. 35 (14-15): 2397–2402. doi:10.1016/S0025-5408(00)00453-0. ISSN 0025-5408.   – via ScienceDirect (Subscription may be required or content may be available in libraries.)