1 8. Chemistry of the Main Group Elements The Group 14 Elements http://www.chemsoc.org/viselements/pages/pertable_fla.htm Carbon (C) non-metal 8. Chemistry of the Main Group Elements The Group 14 Elements - Carbon Isotopes of Carbon: Nuclide Atomic Mass Nat. Abd. Nucl. Spin 12 C 12.000 000 000* 98.90 0 13 C 13.003 354 826 1.10 ½ unstable nuclides Atomic Mass Half life Decay Mode 10 C 10.016 86 19.3 s β + 3.650 MeV 11 C 11.011 43 20.3 m β + (EC) 1.982 14 C** 14.003 241 5730 y β − 0.156 * ) by definition ** ) traces of this isotope occur naturally NMR radio- carbon dating
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Nuclide Atomic Mass Nat. Abd. Nucl. Spin12C 12.000 000 000* 98.90 0 13C 13.003 354 826 1.10 ½
unstablenuclides Atomic Mass Half life Decay Mode10C 10.016 86 19.3 s β+ 3.650 MeV11C 11.011 43 20.3 m β+ (EC) 1.98214C** 14.003 241 5730 y β− 0.156
*) by definition**) traces of this isotope occur naturally
NMR
radio-carbondating
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8. Chemistry of the Main Group Elements
Carbon - Fractionation of Isotopes
13C12C sample
13C12C std
−
13C12C std
x 1000δ13C =
positive δ13C value: sample has a greater proportion of the heavier isotope of carbon, 13C
negative δ13C value: depleted in the heavier isotope
values in 0/00 (per mil, ppt)
standard: carbon contained in calcite from fossils called belemnites from a particular limestone called the Pee Dee Formation (abbrev. as PDB).
8. Chemistry of the Main Group Elements
Carbon – Radiocarbon Dating
14C nat. abd.: 10 −12% τ1/2 = 5730 yβ − 0.156 MeV
in the upper atmosphere: 147N + 10n -> 14
6C + 11H
14C + O2 -> 14CO + O
14CO + •OH -> 14CO2 + H•
Equilibrium of 14CO2 formation and radioactive decay
-> 14CO2/12CO2 global scale steady-state equilibrium hydrosphere & biosphere, photosynthesis etc.
-> 14C/12C atomic ratio = 10 −12
Willard Libby(Nobel 1960)
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8. Chemistry of the Main Group Elements
Carbon – Radiocarbon Dating
…once the exchange ceases (e.g. death of biomaterials), the radioactive clock starts running and the age of an object can be determined from the decreasing 14C/12C ratio.
Radiocarbon age limit : 58,000 and 62,000 years (radioactivity of the residual 14C in a sample is too low to be distinguished from the background radiation)
K-Ar and U decay series are used in dating older objects
8. Chemistry of the Main Group Elements
Carbon - Modifications
+ 1.899 kJ
1500 oC
1500 –1800 oC,53000-100000 bar
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8. Chemistry of the Main Group Elements
Carbon - 3rd Modification in Nature (1985) 318, 162
8. Chemistry of the Main Group Elements
Carbon - 3rd Modification:
US Pavilion @ 1967 Montreal World's Fair by Buckminster Fuller
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8. Chemistry of the Main Group Elements
Carbon - 3rd Modification in Nature (1985) 318, 162
Richard Smalley & Robert F. Curl (left)(died Oct. 28, 2005) Rice University
Sir Harold W. Kroto (University of Sussex, now Florida State)
Nature (1990) 347, 354
8. Chemistry of the Main Group Elements
Carbon - 3rd Modification:
Studying the conditions under which carbon nucleates(in a He-atmosphere)
Hydrazine in a 70% solution is used to power the EPU (Emergency Power Unit) on the F-16 fighter plane.
F-16’s EPU
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8. Chemistry of the Main Group Elements
Nitrogen –Hydrogen Compounds
N2H4: N2H4 + O2 -> N2 + 2H2O
ΔH0= −622 kJ/mol
Reducing agent e.g. in plutoniumextraction from reactor waste
8. Chemistry of the Main Group Elements
Nitrogen Oxides (NOx) & Oxoanions
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8. Chemistry of the Main Group Elements
Nitrogen Oxides (NOx) & Oxoanions
N2O: mild dental anestheticenvironmentally acceptablesubstitute for FClC’sNO: TM ligand very reactive, toxic gas, and yet,…biologically important: NO Synthases: nNOS, iNOS, andendothelial NOS (lumen bloodvessels)
NH2
C NH2
NH(CH2)3
CHNH2
COOH
NOS
2NADPH
2O2
NH2
C O
NH
(CH2)3
CHNH2
COOH
+ NO
2NADP
2H2O
arginine citrulline
8. Chemistry of the Main Group Elements
Nitrogen Oxides (NOx) & Oxoanions
NO: …biologically important
Blood Flow: NO relaxes smoothmuscles in blood vessels.
Birth: NO inhibits contractilityof smooth muscle wall of uterus.
Kidney function: NO increasesblood flow in kidney cells thus,increasing rate of filtration.
Inflammation: No inhibits in-flammation in blood vessels.
Secretion: NO affects secretionfrom several endocrine glands.
and, and, and…
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8. Chemistry of the Main Group Elements
Nitrogen Oxides (NOx) & Oxoanions
NO2: in equilibrium w/ N2O4
can be formed in atmosphere(e.g. lightning on N2 & O2)forms via combustion of fossilfuels -> “acid rain”
3NO2 + H2O -> 2HNO3 + NO
HNO3: for NH4NO3 mass prod.
2NH4NO3 -> 2N2 + O2 + 4H2O+ ΔE
fertilizer & explosives
Fritz Haber, Nobel Prize 1918for “potatoes from air”
NH3 + O2 + cat -> NO + air + H2O -> HNO3 -> NH4NO3 (explosives)
8. Chemistry of the Main Group Elements
Nitrogen Oxides & Oxoanions
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8. Chemistry of the Main Group Elements
Nitrogen Oxides, Oxoanions & Acids
8. Chemistry of the Main Group Elements
Nitrogen – Rich Redox Chemistry
moststable
leaststable
good playground to practice formaloxidation states…
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8. Chemistry of the Main Group Elements
…a little bit of Phosphorous Chemistry: stable polymers
red phosphorus
black phosphorus
no allotrope,but mixture:
violetphosphorus
Hittorf’s P
8. Chemistry of the Main Group Elements
…a little bit of Phosphorous Chemistry: stable polymers
black P (~ graphite)
violet P
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8. Chemistry of the Main Group Elements
…by far the most exciting allotrope: monomeric P4
White Phosphorus P4(g) W P2(g)
very toxic & reactive with air (O2) α-form (cubic) condensation from gas phase, slowly transformsto β-P4 (above −76.9oC)
@ 1070K
221
ppm
8. Chemistry of the Main Group Elements
…a little bit of Phosphorous Chemistry:
Very toxic & reactive with air White Phosphorus (P4)α-form (cubic) condensation from gas phase, slowly transformsto β-P4 (above −76.9oC)
Description :A colorless, odorless gas that is totally unreactive. It is extracted from natural gas wells, some of which contain gas that is 7% helium. It is used in deep sea diving for balloons and, as liquid helium , for low temperature research. The Earth’s atmosphere contains 5 parts per million by volume, totaling 400 million tons, but it is not worth extracting it from this source at present.
Discovered : by Sir William Ramsay in London, and independently by P.T. Cleve and N.A. Langlet in Uppsala, Sweden in 1895
Discovered : by Sir William Ramsay and M.W. Travers in 1898 (London, UK)
Origin : Greek ‘neos’ (new)
Description :A colorless, odorless gas that comprises 18 parts per million of air. Neon will not react with any other substance. It is produced from liquid air for ornamental lighting (i.e. neon signs) because it glows red when an electrical discharge is passed through it.
Discovered : 1899 by Lord Rayleigh and Sir William Ramsay
Origin : Greek ‘argos’meaning inactive.
Description :The third most abundant gas, making up one percent of the atmos-phere. The quantity has increased since the Earth was formed because radioactive potassium turns into argon as it decays. Argon is a colorless, odorless gas that is totally inert to other substances, and for this reason it is ideal in light bulbs.
Discovered : by Sir William Ramsay and M.W. Travers in 1898
Origin : Greek ‘kryptos’, meaning hidden
Description :A colorless, odorless gas that is inert to everything but fluorine gas. The isotope krypton 86 has a line in its atomic spectrum that is now the standard measure of length : 1 meter is defined as exactly 1,650,763.73 wavelengths of this line. Krypton is one of the rarest gases in the Earth’s atmosphere, accounting for only 1 part per million by volume.
Discovered : by Sir William Ramsay and M.W. Travers in 1898
Origin : Greek ‘xenos’, meaning strange.
Description :A colorless, odorless gas that makes up 0.086 parts per million of the atmosphere. About half a ton a year is produced from liquid air and used for research purposes.