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02.2 Bohr‘s Atomic Theory 02.3 Notations Nucleus: Protons Neutrons Electron Orbits: Electrons Nucleon Number Notation: φ = 10-7 - 10-10 m Neutron (+) (n) Atomic Number Nucleon Number Proton (-) Nuclides at present about 2500 types of different atoms – so called nuclides – are known, they form 114 different chemical elements, only 274 nuclides are stable ! Chemical Elements fundamental substance that cannot be further refined or subdivided by chemical means. All atoms of a chemical element have the same number of protons. Proton Number Element 1 1 1 H 1 4 2 4 He 2 12 6 12 C 6 03.1 Chart of Nuclides 03 Atoms – Nuclides - Elements Atoms particles that form matter Element Isotopic Nuclides Atoms which have the same atomic number but different mass numbers He He-3 He-4 He-5 He-6 4,002602 0,000137 99,99986 99,99986 806,7 ms 3β− n σabs < 0,05 σ 0,00005 0,02 H H-1 H-2 H-3 1,00794 99,985 0,015 12,323 a σ 0,332 σ 0,332 σ 0,00052 β- 3,5 Z β− 0,02 n1 10,25 m β− 0,8 N 1 03.2 Nuclid Categories 03.3 Chart of Nuclides - FZ Karlsruhe Isotopic nuclides Atoms which have the same atomic number but different mass numbers Isobaric nuclides Atoms which have the same mass number but different proton numbers Isotonic nuclides Atoms which have the same neutron number but different proton numbers Isomeric nuclides Atoms which have the same proton and neutron numbers but different energy levels 03.4 Chart of the Nuclides 03.5 Chart of the Nuclides TOICD (1) legend Karlsruhe Chart of Nuclides: all known nuclides X axis: number of protons Y axis: number of neutrons Colours and symbols: stable nuclides positron decay β+ electron capture ε negatron decay β- alpha decay α spontaneous fission sf proton decay p isomer decay Iγ 2 03.7 Hydrogen Isotopes 03.6 Chart of the Nuclides TOICD (2) 1 1 Hydrogen 2 1 3 1 04 The Standard Model 04.1 Elementary Particles & Quarks Elementary Particles Matter Atom Nucleus Electron Proton Neutron Quark Leptons light particles Mesons even quark numbers Neutrinos ... Elektrons ... Baryons heavy particles Hyperons ... Bosons "force particles" Nucleons Neutrons Protons Quarks Quarks Photons ... 3 04.2 Leptons - light particles name symbol Electron Müon Tau eµτ- e+ µ+ τ+ rest mass [MeV] charge 0,511 105,6 1784 -1 +1 -1 +1 -1 +1 spin mean lifetime [s] 1/2 1/2 1/2 stable 2. 10-6 3. 10-13 04.3 Mesons name symbol Pionen 135 Kaonen π0 π+ π− K0K0 Pionen rest mass [MeV] 2 quark particles charge 0 140 +1 -1 498 0 0 494 +1 -1 quark sequences spin mean lifetime [s] uu dd 0 8.10-17 ud du 0 2,6 .10-8 ds d s 0 10-10 -5.10-8 us 0 1,2.10-8 Electron- Neutrino νeνe ? 0 0 1/2 stable ? Kaonen K+ Müon-Neutrino νµνµ ? 0 0 1/2 stable ? J / Psi J/Ψ 3098 0 cc 1 1.10-20 Tau-Neutrino ντ ντ ? 0 0 1/2 stable ? D-Null D0 1863 0 cu 0 1.10-12 D-Plus D+ 1863 1 cd 0 4.10-13 Ypsilon Y 9460 0 bb 1 1.10-20 leptons + quarks = fundamental structures of matter 04.4 Baryons name symbol rest mass [MeV] Proton p p 938,3 Neutron n n 939,6 Lambda Λ Λ 1115 Sigma-Plus Σ+ Σ+ 1189 Sigma-Minus Σ− Σ− 1197 Sigma-Null Σ0 Σ0 1192 Xi-Minus Ξ− Ξ− 1321 Xi-Null Ξ0 Ξ0 1315 Omega-Minus Ω−Ω− 1672 Charm-Lambda Λc Λc 2280 heavy particles charge +1 0 0 +1 -1 0 -1 0 -1 +1 -1 0 0 +1 -1 0 1 0 -1 +1 quark sequences u u d uud d d u ddu u d s uds u u s uus d d s dds u d s uds d s s dss u s s uss s s s sss u d c udc spin mean lifetime [s] ½ stable ½ ca. 900 ½ 2,6.10-10 ½ 8.10-11 ½ 1,5.10-10 ½ 6.10-20 ½ 1,6.10-10 ½ 3.10-10 ½ 8.10-11 ½ 2.10-13 K− 04.5 Eichbosons - name symbol rest mass [MeV] su exchange particles charge spin mean lifetime [s] Photon W-Teilchen Z-Teilchen Gluon γ W + W− Z g ? ~83 000 ~93 000 0 0 1 0 0 1 -1 1 1 stable 10-25 10-25 stable exchange particles: force transmitters 4 04.6 Quarks - 04.7 „Visual“- Quarks particle „substructures“ name symbol rest mass [MeV] charge up down strange charm bottom (beauty) top (truth) u u d d s s c c b b t t ~5 ~10 ~100 ~1500 ~4700 ? 2/3 -1/3 -1/3 2/3 -2/3 1/3 1/3 -2/3 -1/3 1/3 2/3 -2/3 spin mean lifetime [s] ½ ½ ½ ½ ½ ½ top up stable variable variable variable variable variable down bottom strange charm 3 quark elementary particles : baryons 2 quark elementary particles : mesones 05 Antimatter • All elementary particles have antimatter counter parts, antimatter counterparts have the same mass but opposite electric charges • When matter and antimatter come in contact they are instantly converted to energy (annihilation) and photons or mesons were created, respectively • Photons are identical with its antimatter. 06 Stable and Instable Nuclides nucleon mass [g] relative charge spin t1/2 atomic mass beta decay [u] Proton 1,672 x 10-24 1,00728 +e Neutron 1,674 x 10-24 1,00867 0 1 1 2 h stable 2 h 12 min 1 u = 1,660 x 10-24 g = 931,5 MeV 5 06.1 Mass Defect Mass defect is the mass difference between the nuclide rest mass and the free nukleon rest masses. 06.2 Nucleus Binding Energy Mean Binding Energy per Nucleon Mass defect is proportional to the nucleon bonding energy. alpha particle mass defect: ∆m = malpha ∆m = 4,00151 ≅ 28 MeV - (2 x mproton - 2x mneutron) - (2 x 1,00782 + 2 x 1,00866) = 0,0307u Mass Number 06.3 Radioactivity • • • • 06.4 Activity Radioactivity is the ability of an unstable atomic nucleus to transform into a stable product or another unstable product while emitting radiation. This transformation and emission of energy is called radioactive decay. A transformation from one element to another is known as a transmutation. The radiation can be emitted in several forms, including: The becquerel (symbol Bq) is the SI derived unit of radioactivity, defined as the activity of a quantity of radioactive material in which one nucleus decays per second. It is therefore equivalent to s-1. The older unit of radioactivity was the curie (Ci). a positively charged alpha particle (α), which is the same as a helium nuclei consisting of two neutrons and two protons a negatively charged beta minus particle (β-), which is the same as an electron a positively charged beta plus particle (β+), which is the same as a positron, a particle of equal mass but opposite charge of an electron a gamma ray (γ), which is a photon, a particle with a exceedingly high wave frequency and energy (visible light and radio waves are also photons, as well as all other electromagnetic radiation). An additional radioactive process is nuclear fission, where some elements can split as a result of absorbing an additional neutron 1 Gramm Radium-226: 37 .109 disintegrations per second 37 .109 Bq = 1 Curie (Ci) 6 06.5 The Radioactive Decay A exponential decay A t½ t 06.6 The Decay Law Activity half life time A(t )= A0 ⋅ e t½ t The half-life of a radioactive isotope is the time it takes for half of the atoms in a pure sample of the isotope to decay into another element. It is a measure of the stability of an isotope; the shorter the half life, the less stable the atom. The decay of an atom is said to be spontaneous as one can only determine the probability of decay and not predict when an individual atom will decay 06.7 Decay Examples Radionuclide Occurancy Decay Type Tritium Ra - 226 I - 131 Cs - 134 U - 235 U - 238 0,00013 % β α/γ β- / γ β/γ 0,720 % α, β−, γ, sf * 99,28 % α, β−, sf * sf means spontaneous fission 12,346 1,6 . 103 8,04 2,06 2,09 7,030 . 108 4,468 . 109 ln 2 ⋅t t1 / 2 = Activity after t = time = Activity at t = t0 = half life 06.8 The Natural Acivity of a Standard Person (20 - Half Life t1/2 - A(t) t A0 t½ − a a d a h a a Radionuclide Activity in Bq K - 40 4 500 C -14 3 800 Rb - 87 650 Pb - 210, Bi - 210, Po - 210 60 Daughters Rn - 220 30 H-3 25 Be - 7 25 Daughters Rn - 222 15 Others 7 Sum 9 112 (ca. 230 Bq / kg) 30 y, 7 0 kg) 7 06.9 Spezific Activity in Food Food KCl salt Vegetarian food Reindeer liver (Po-210) Brazil nut (Ra- 226) Activity in Bq / kg 15 944 40* 222 132 Food 120 g bread 25 g camenbert 25 g corned beef 20 g Nutella 125 ml black tea (Turky) Activity in Bq 2,0 0,9 1,2 3,2 6,5 Nicht verkehrsfähig ! 100 g cottage cheese 25 g blue berries * average 06.11 Activity of a Lunch Food Activity in Bq 150 g wild animal meat (Niedersachsen) 87,2 60 g pasta 0,6 200 g Marones (Niedersachsen) 210,6 Not permitted ! 20 g canned peach 10 g red berries (Skandinavia) 150 g vanilla ice cream 50 g cherries 06.10 Activity of a Breakfast 1,0 0,0 3,0 16,7 0,2 2,4 07.4 Shell Model of the Nucleus • Strong Interaction Models – strong nucleon interactions – strong perturbations with movements • Independant Particle Models – weak nucleon interactions – no perturbations, independent movements – shell model: analog electron shells – 2(2l+1) nucleons per shell – bonding energy approximatively independent from shell number – no force center but potential minimum – strong interactions between spin and orbital rotations 8 07.6 The 4 Fundamental Forces 08 Nuclear Physics Nuclear Fission • electromagnetic force uranium + 1 neutron Ö disintegration • gravitational force • strong nucleus interactions (ca. 2,0 x 10-13 cm reach) nucleon bonding • weak nucleus interactions (ca. 0,5 x 10-13 cm reach) quark bonding causes radioactiv decay ! 08.1 Nuclear Chain Reaction 08.2 Fission Product Yields Fission Yield U-235 Nuclear Fission U-235 + 1n Ø Fission Products + 2.3 n Mass Number 9 09.1 Artificial Nuclear Reactions 09 Nuclear Reactions α,N reactions e-, He++ capture 0 −1 e + → 40 19 K 40 18 Ar n capture 1 0 n + B → 10 5 Li + 7 3 4 2 13N 13C 14N + 1H + 1H 15O 15N + 1H → → → → → → 13N +γ 13C + e+ + ν e 14N + γ 15O + γ 15N + e+ + ν e 12C + 4He + 1,95 MeV + 1,37 MeV + 7,54 MeV + 7,35 MeV + 1,86 MeV + 4,96 MeV 14 7 N → 18 93 F → O + 17 8 1 1 p He + γ Bethe-Weizsäcker Cycle + 1H He + 4 2 09.2 The CNO (carbon-nitrogenoxygen) Cycle 12C 14N(α,p)17O Lebensdauer 1,3·107 Jahre 7 Minuten 2,7·106 Jahre 3,2·108 Jahre 82 Sekunden 1,12·105 Jahre 09.3 The Proton Proton (PP) Reaction 1H + 1H e+ + e2H + 1H 3He +3He 3He + + e7Li + 1H 7Be 3He 7Be While the proton-proton chain is more important in stars the size of the sun or less, theoretical models show that the CNO cycle is the dominant source of energy in heavier stars. The cycle results in the fusion of four hydrogen nuclei (1H, protons) into a single helium nucleus (4He, alpha particle), which supplies energy to the star in accordance with Einstein's equation. Ordinary carbon serves as a catalyst in this set of reactions and is regenerated (3,4·108 y) 4He 8B 8Be 4He + + 1H → → → → 2H + e+ + νe 2γ 3He + γ 4He + 1H + 1H → → → 7Be → → → ↔ 7Be +γ + νe 4He + 4He + 0,42 MeV + 1,02 MeV + 5,49 MeV + 12,86 MeV 10–14 106 Kelvin 7Li +γ +γ 8Be + e+ + ν e 4He + 4He 14–23 106 Kelvin 8B >23 106 Kelvin The proton-proton chain reaction is one of two fusion reactions by which stars convert hydrogen to helium, the other being the CNO cycle. The proton-proton chain is more important in stars the size of the Sun or less 10 Atomic Physicists Hans Bethe Niels bohr John Chadwick Marie Curie Pierre Curie Paul Dirac Albert Einstein Otto Hahn Liese Meitner Max Planck Robert Oppenheimer Ernest Rutherford Snyder Arnold Sommerfeld Fritz Straßner Carl Friedrich von Weizäcker Exercises (1) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Exercises (2) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. What are nucleons ? Which nucleons you know ? Wxplain the quark structure of protons ? Which elementary particles type are electrons, protons, neutrons ? What is the design of the antiproton ? What is the design of the antiphoton ? What are quarks ? Explain the mass defect ! Which are the 4 fundamental forces ? What is nuclear fusion ? Which nuclides are favorised ? What is nuclear fission ? Which nuclides are favorised ? What are the conclusions from the RUTHERFORD experiment ? What is the definition of the atomic number ? What is the definition of the mass number ? Which are the three hydrogen isotopes ? Do the hydrogen isotopes show different physical properties ? Why ? Do the hydrogen isotopes show different chemical properties ? Why ? What are isomeric nuclides ? How many electrons can be filled in the L-shell ? What is a stationary wave ? What is an electron orbital ? References 1. 2. 3. 4. 5. B. Bröcker; DTV-Atlas zur Atomphysik; DTV-Verlag, 1993 R.B. Firestone; CD: Table of Isotopes; Wiley-Interscience, 1996 S. Hawking; CD: Eine kurze Geschichte der Zeit; Navigo, 1997 B. Bröcker; DTV-Atlas zur Atomphysik; DTV Verlag 1993 P.M. Magazin 12 / 94 Bild der Wissenschaft 11 / 1996 11 Web-Links http://atlasinfo.cern.ch/Atlas/documentation/EDUC/physics1.html http://users.senet.com.au/~rowanb/chem/atstruct.html http://newton.ex.ac.uk/aip/physnews.412.html#1 Add literature 12