The elements in group 15 Nitrogen Phosphorus Arsenic Antimony Bismuth.
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Transcript of The elements in group 15 Nitrogen Phosphorus Arsenic Antimony Bismuth.
The elements in group 15Nitrogen
PhosphorusArsenic
AntimonyBismuth
Introduction• All are important elements• Increasing trend to metallic character and
cationic behavior from top to botom in the grroup
• Nitrogen is different with the other elements, even phosphorus
1. The diminished ability to form p-p π bond: radius, single bond
2. The possibility of utilizing the d orbitals: d-p π bond , CN
Introduction (continue)
• All , but Bi, are important donor atoms in their trivalent compounds
• Bismuth is a metal element, but sodium bismuthate is a very strong oxidizing agent: inert electron pair effect
Occurrence and Recovery of the Elements
Phosphorus
Principally obtained from phosphate rock-remains of fossilized life forms
Ca5(PO4)3F and Ca5(PO4)3OH
Ca5(PO4)3F(s) + H2SO4(I) 3H3PO4(l) + 5CaSO4(s) + HF(aq)
2Ca3(PO4)2 + 6SiO2 + 10C 6CaSiO3 + 10CO + P4
1500 °C
Elemental Phosphorus
White Phosphorus
Black Phosphorus
White Phosphorus:
• Reaction on previous slide• Ignites spontaneously in air
• Stored under water
Red Phosphorus:
•Heat white phosphorus at 300 C in inert atm for several days•Does not ignite in air•Structure: contain linear chain
Black Phosphorus•The most stable form
•Formed when P heated under high pressure.
Occurrence and Recovery of the Elements
Arsenic
Arsenic is found in nature in a number of minerals including
realgar (As4S4)
orpiment (As2S3)
arsenolite (As2O3)
iron minerals such as arsenopyrite (FeAsS) loallingite (FeAs2).
Arsenic is made on an industrial scale by heating appropriate minerals in the absence of air. The arsenic is condensed out as a solid.
FeAsS (700°C) FeS + As(g) + As(s)
Occurrence and Recovery of the Elements
Antimony
Antimony is found in nature in a number of minerals including
stibnite (Sb2S3)
ullmanite (NiSbS). Small amounts of native antimony have been found. Some ores are treatable under reducing conditions to form Sb2S3.
The sulphide is removed to leave elemental antimony with scrap iron.Sb2S3 + 3Fe 2Sb + 3FeSIn antehr process, some ores can be heated to evolve the oxide Sb2O3 and this in turn can be reduced by charcoal in
the presence of sodium sulphate, to ensure mixing, to form elemental antimony.
2Sb2O3 +3C 4Sb + 3CO2
Occurrence and Recovery of the Elements
Bismuth
Bismuth is found in nature largely as bismite (Bi2O3)
bismuthinite (Bi2S3)
bismutite [(BiO)2CO3].
However it is generally made as a byproduct of copper, lead,tin, silver, gold, and zinc plants. The final step involves a reduction of the oxide by charcoal.
Phosphine PH3
Typically prepared by the action of dilute acid on calcium or aluminum phosphide or by pyrolysis of H3PO3 or by reaction of KOH on white phosphorus
Pure phosphine is not spontaneously flammable but often inflames due to the presence of trace P2H4 or P4
•Readily oxidized by air once ignited•Sparingly soluble in water•Very weak base pKb 1E-25 PH4
+ is readily hydrolized
Extremely poisonous
Only phosphine of the lower Group 15 elements forms subhydrides - P2H4
Used as a semiconductor dopant source
Arsine AsH3
Even more poisonous than phosphine
Readily decomposes to yeild elemental arsenic-”arsenic mirror test”
Only know use as a semiconductor dopant source
Stibine SbH3 and Bismuthine BiH3
Limited stability makes these compounds of little interest•Bond energy (stability): NH3 >PH3 > AsH3 > SbH3 > BiH3
•Bond angle (HAH): NH3 >PH3 > AsH3 > SbH3 > BiH3
•Base strength in water: same as above•Reduce ability: NH3 <PH3 < AsH3 < SbH3 < BiH3
Compounds of Group 15 ElementsHalides: PX3 PX5
Phosphorus Fluorides
PF3
colourless gas •Melting point: -152°C •Boiling point: -102°C
P2F4
colourless gas •Melting point: -86.5 •Boiling point: -6.2
PF5
colourless gas •Melting point: -94°C •Boiling point: -85°C
2PCl3(l) + 3ZnF2(s) 2PF3(g) + 3ZnCl2(s)
Compounds of Group 15 Elements
Halides:
Arsenic Fluoridescolourless liquid
•Melting point: -6°C •Boiling point: 63°C
AsF3
“Bridged” structure, but essentially molecular
AsF5 colourless gas •Melting point: -79.8°C •Boiling point: -52.8°C
Compounds of Group 15 Elements
Other Halides
Colourless liquid •Melting point: -16°C •Boiling point: 130°C
AsCl3 Decomp at –50 °C Recall BrO4
–
AsCl5
white to pale yellow crystalline solid
Melting point: 31°C
Boiling point: 221°C
AsBr3
red crystalline solid •Melting point: 141°C •Boiling point: 400°C; 424°C
AsI3
Compounds of Group 15 Elements
Halides:
Antimony Fluorides
•colourless crystalline solid •Melting point: 290°C •Boiling point: 345°C
SbF3
SbF5 •viscous liquid •Melting point: 8.3°C •Boiling point: 141°C
Actual structure has intermolecular contacts giving highly distorted octahedral coordination
Forms tetrameric structure in the solid state
AsF3 and SbF3 are very useful as fluorinating agents
Compounds of Group 15 Elements
Other Halides
colourless or yellow liquid •Melting point: 4°C •Boiling point: 140°C •Why liquid when trichloride a solid?
SbCl5
red crystalline solid •Melting point: 170.5°C •Boiling point: 401°C
SbI3
SbBr3 white or yellow solid, deliquescent crystals •Melting point: 96°C •Boiling point: 288°C
white crystalline solid, deliquescent
•Melting point: 73.4°C •Boiling point: 223°C
SbCl3
Compounds of Group 15 Elements
Halides:
Bismuth Fluorides
grey-white crystalline solid •Melting point: 649°C •Boiling point: 900°C
BiF3
BiF5
white crystalline solid •Melting point: 154°C •Boiling point: 230°C
What do the m.p. and b.p. imply?
What do these m.p. and b.p imply?
Ionic lattice
Infinite linear BiF6 chains
Compounds of Group 15 Elements
Other Halides NonexistantBiCl5
green-black crystalline solid •Melting point: 408.6°C •Boiling point: 542°C
BiI3
BiBr3 •yellow, golden crystalline solid, deliquescent
•Melting point: 219°C •Boiling point: 462°C
•white or yellowish white crystalline solid,
•Melting point: 233.5°C •Boiling point: 441°C
BiCl3
Bismuth Bromide Structure
O2Cl3PO PCl3
RMgX, LiRPR3, PR2Cl, PRCl
AgNCOAgSCN
P(NCO)3 P(NCS)3H2O
HCl + H3PO3 + H4P2O5
N2O4
Cl3P=NPCl2O
RH + O2
RPOCl2 + HClRCl + AlCl3
[RPCl3]+[AlCl4]-
H2O
RPOCl2
NH3
P(NH2)3
Ni(CO)4
Ni(PCl3)4
ROHP(OR)3 in base(RO)2PHO in absence of base
RMgX
R3PO
ROH(RO)2PO
S
Cl3PS RCO2H
RCOCl+ H3PO3
Reactions of PCl3
Reactions ofother MX3
Halides similar
Oxides of P, As, Sb and Bi
P4O10 a good drying and detergent agent
P4 + 5O2 P4O10
Prepared by burning P in air
Limit the supply of oxygen and:
P4 + 3O2 P4O6
P4O10 + 6H2O 4H3PO4
P4O6 + 6H2O 4H3PO3
How to make an acid
Oxides of Arsenic, Antimony and Bismuth
Only As and Sb for (V) oxides, these are of limited stability.
As, Sb and Bi oxides primarily (III) oxidesAs2O3 Sb2O3 Bi2O3
Note: Acid-base property Oxide-reduce property
Gas Phase of As and Sb oxides:
Sulphide
• P4S3 P4S5 P4S7 P4S10… similar as oxides• Exclude P4S10, all contain at least one P–P
bond• As2S3 As2S5 As4S4 …• Sb2S3 Sb2S5
• Bi2S3 why ?• Note:1. Color: yellow to black. polarization covalent2. Solubility and oxidizing-reduce properties3. Reaction with H+, OH–, S2–, Sx
2–
Phosphorus Oxoanions:
Oxidation Number
Formula Name Structure Remarks
+1 H2PO2- Hypophosphit
eFacile
Reducing Agent
+3 HPO32- Phosphite Facile
Reducing Agent
+4 P2O64- Hypophosphat
eBasic
+5 PO43- Phosphate Strongly Basic
+5 P2O74- Diphosphate Basic
Chain variations
P
H
H OO
P
H
O OO
PO
OO
PO
OO
P
O
O OO
PO
OO
PO
OO
O
Structure and acidic strength of H3PO3
• Pauling rule:
1. HnROm: represented as ROm-n(OH)n
2. pK = 7 – 5(m – n)
3. In same type: electronegativity• Application:
1. H3PO3 P(OH)3 pK = 7
2. Experimental: pK = 2
3. H3PO3 HPO(OH)2
• P(OR)3
Poly- and cycle-phosphoric acid(pyrophasphoric acid)
• [PnO3n+1](n+2)–
Ex. Na5P3O10
• [PnO3n]n–
• Ex. Na5P3O9
• Note:
1. Solubilities of different phasphorates2. Reducing properties of Hypo-/phosphite
Phosphorus Nitrogen Compounds
The extra valence in N can make for some interesting structures - Phosphazenes
P
PP
P
N
NN
N
N N
R
R
RR
R
R
PCl5 + nNH4Cl (Cl2PN)n + 4nHCl
(Cl2PN)n + 2nCF3CF2O- [(CF3CF2O)2PN]n + 2nCl-
Substitutions by other Lewis bases are common
Polymeric structures common – rubber-like substances
-excellent low temperature properties
Hexachlorotriphosphazene
• planar• N sp2, P sp3 • d-p π • May form
polylimer
Complexes
• PF6– AsF6
– SbF6–
• NaSb(OH)6
• KH[Sb2(d-C4H2O6)2]
• Common for Bi3+
• Bi6O66+ Bi6O6(OH)3
3+
Bi6O6(OH)6