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NUCLEAR CHEMISTRY

NUCLEAR CHEMISTRY. NUCLEAR ENERGY. İs it GOOD. Or BAD?. At the end we can only see the little part of iceberg. Outline History of Nuclear Energy Uranium was discovered in 1789 by Martin Klaproth , a German chemist, and named after the planet Uranus.

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NUCLEAR CHEMISTRY

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  1. NUCLEAR CHEMISTRY

  2. NUCLEAR ENERGY

  3. İs it GOOD Or BAD?

  4. At the end we can only see the little part of iceberg.

  5. Outline History of Nuclear Energy • Uranium was discovered in 1789 by Martin Klaproth, a German chemist, and named after the planet Uranus. • The science of atomic radiation, atomic change and nuclear fission was developed from 1895 to 1945, much of it in the last six of those years. • Over 1939-45, most development was focused on the atomic bomb. • From 1945 attention was given to harnessing this energy in a controlled fashion for naval propulsion and for making electricity. • Since 1956 the prime focus has been on the technological evolution of reliable nuclear power plants.

  6. Ionising radiation was discovered by Wilhelm Rontgen in 1895, by passing an electric current through an evacuated glass tube and producing continuous X-rays. Then in 1896 Henri Becquerel found that pitchblende (an ore containing radium and uranium) caused a photographic plate to darken. He went on to demonstrate that this was due to beta radiation (electrons) and alpha particles (helium nuclei) being emitted. Villard found a third type of radiation from pitchblende: gamma rays, which were much the same as X-rays. Then in 1896 Pierre and Marie Curie gave the name 'radioactivity' to this phenomenon, and in 1898 isolated polonium and radium from the pitchblende.

  7. Discovery Henry Becquerel- In 1896 French scientist who discovered naturally occurring radiation He left uranium ore in a drawer with film. When the film was developed there was an image of the Uranium decaying

  8. Marie Sklodowska Curie Named Radioactivity, Radium, Polonium, discovered several elements

  9. The Nucleus • Remember that the nucleus is comprised of the two nucleons, protons and neutrons. • The number of protons is the atomic number. • The number of protons and neutrons together is effectively the mass of the atom.

  10. Isotopes • Not all atoms of the same element have the same mass due to different numbers of neutrons in those atoms. • There are three naturally occurring isotopes of uranium: • Uranium-234 • Uranium-235 • Uranium-238

  11. For an ordinary chemical reactions valence electrons are exchanged or shared. No change is observed in the nucleus of an atom .

  12. RADIOACTIVITY • In nature without any external effect unstable atomic nucleus emits charged particles and energy. This process is radioactivity. The atoms that show this property are radioaisotopes, and the rays are known to be radioactive rays. • Any radioactive atom in any compound produces a radioactive compound.

  13. DIFFERENCES BETW. CHEMICAL RXNS AND NUCLEAR RXNS • CHEMICAL RXNS • Depends on the environmental conditions • Electron arrangements of atoms will change , but there is no change inthe atomic nucleus, • The kind and the number of atom conserved, • Mass is conserved, • Amount of energy gained or lost is not too much. • NUCLEAR RXNS • Does not depend on the environmental conditions(temperature, pressure, catalyst,..) • Structure of nucleus will be changed, • The kind and the number of atom may change, • Mass is not conserved. • Huge amount of energy attend.

  14. What is the smallest subatomic particle of the matter ??? • In the recent years, accelerators used to get more information about particles. • In these study neutrons and protons were made to collide by accelerators. CERN is one of these accelerators.

  15. Protons are accelerated by electromagnets and with high amount of speed do collisions with neutrons. • Particles produced at the end of the collisions investigated by looking through the signs that leave at the detectors.

  16. Each element is an atomAtoms are not elementary particles

  17. Particle Size Scale

  18. galaxy cell nucleus Most important detector Source target Electron microscope detector accelerator

  19. STANDARD MODEL Explains • how subatomic particles were arranged • Structure of nucleus • Attractive forces between them. • Up until now • Smallest particle is determined as quarks.

  20. STANDARD MODEL • Elemental particles we classified into 2 • Quarks • Leptons There are : • 6 types of quarks • 6 types of leptons • Anti quarks and anti leptons

  21. STANDARD MODEL • QUARKS • Name of particle Symbol Charge • Up quark u +2/3 • Down quark d -1/3 • Charm quark c +2/3 • Strange quark s -1/3 • Top quark t +2/3 • Bottom quark b -1/3

  22. QUARKS • Anti-quarks are shown by putting line on the symbols. • Their electrical charges are the opposite of the quark.

  23. PROTONS AND NEUTRONS • Protons formed by 2 up and 1 down quark so its electrical charge: • 2 / 3 + 2 / 3 - 1 / 3 = + 1 • Neutrons are formed by 2 down and 1 up quark. so its electrical charge: • 2 / 3 - 1 / 3 - 1 / 3 = 0

  24. LEPTONS There are 6 types: Particle Symbol Charge • Electron e- -1 used for electrical and chemical attractions • Muon - -1 Heavier and more unstable than electrons • Tau - -1 Heavy and very unstable particle

  25. LEPTONS • Electron neutrino e 0 Continuosly passing through our body. • Muon neutrino µ0 Obtained from some of the decays • Tau neutrino  0 It is not observed yet.

  26. LEPTONS • First three of the leptons have anti-particles: • Anti-electron : it is known as positron, it has positive charge its spin and mass is the same as electron. • Anti-muon • Anti-tau

  27. NUCLEAR FORCES Big Idea of Science: There are only four known forces in nature: • Gravity • Electromagnetism • Weak Nuclear Force • Strong Nuclear Force

  28. NUCLEAR FORCES • Two protons more than 10-15m will repel each other by their like charges. • Inside a nucleus, the distances are small enough that the strong nuclear force overcomes the weak repulsive force, holding the protons and neutrons together.

  29. NUCLEAR FORCES • Weak Nuclear Forces • Particles with like charges repel. • This causes electrons to orbit around the nucleus.

  30. NUCLEAR FORCES • Strong Nuclear Forces • Particles in the nucleus actually are held together by an even stronger attractive force. • Acts only at very short distances (about 10-15m)—beyond this distance, the strong nuclear force is negligible.

  31. Think about it… • How might a higher number of neutrons change the balance between the repulsive and attractive forces in a nucleus? • How might a lower number of neutrons affect this same balance?

  32. NUCLEAR STABILITY • The stability of an atom is the balance of the repulsive and attractive forces within the nucleus (strong and weak force in equilibrium).

  33. NUCLEAR STABILITY • If the attractive strong forces prevail, the nucleus is stable. • If the repulsive weak forces outweigh the attraction of the strong forces, the nucleus is unstable.

  34. NUCLEAR STABILITY • For elements with low atomic numbers, atoms are stable when their neutron to proton ratio is close to one (1:1). • As atomic number increases, stable atoms have ratios greater than one (1:1.5). • This is because at higher atomic numbers, more neutrons are needed to counteract the repulsive forces between the protons.

  35. NUCLEAR STABILITY • The shaded cluster is the “band of stability.” • The solid line represents a neutron-to-proton ratio of 1:1. • Nuclei to the right of the band of stability don’t have enough neutrons to remain stable. • Nuclei to the left of the band have too many neutrons to remain stable.

  36. NEUTRON-PROTON RATIOS • Any element with more than one proton (i.e., anything but hydrogen) will have repulsions between the protons in the nucleus. • A strong nuclear force helps keep the nucleus from flying apart. • Neutrons play a key role stabilizing the nucleus. • Therefore, the ratio of neutrons to protons is an important factor.

  37. NEUTRON-PROTON RATIOS For smaller nuclei (Z  20) stable nuclei have a neutron-to-proton ratio close to 1:1.

  38. NEUTRON-PROTON RATIOS As nuclei get larger, it takes a greater number of neutrons to stabilize the nucleus.

  39. STABLE NUCLEI The shaded region in the figure shows what nuclides would be stable, the so-called belt of stability.

  40. RADIOACTIVE DECAY • Unstable atoms will spontaneously transform until they reach a stable configuration. • These transformations are accompanied by releases of energy.

  41. RADIOACTIVE DECAY • This energy, given off in waves from an atom, is known as radiation. • Substances that give off radiation are called radioactive. • The process of isotopes emitting particles and energy to become more stable is called radioactive decay.

  42. RADIOACTIVE DECAY • Main types of radioactive decay: • Alpha emission • Beta emission • Positron emission • Gamma emission • Electron capture

  43. RADIOACTIVE DECAY Alpha emission (α) • Nucleus emits an alpha particle—two protons and two neutrons • Equivalent to a helium nucleus (He). Alpha Decay Animation http://ie.lbl.gov/education/glossary/AnimatedDecays/AlphaDecay.html

  44. RADIOACTIVE DECAY Beta Emission (β) • Nucleus emits an electron, and a neutron is converted to a proton. Beta Decay Animations: http://ie.lbl.gov/education/glossary/AnimatedDecays/Beta-Decay.html

  45. RADIOACTIVE DECAY Positron Emission • Nucleus emits a positron (identical to an electron in mass, but has a positive charge) • Positron is formed when a proton converts to a neutron.

  46. RADIOACTIVE DECAY Gamma emission (γ) • Nuclei seeking lower energy states emit electromagnetic radiation, which is in the gamma ray region of the electromagnetic spectrum. • Rays are emitted in conjunction with another type of decay (alpha or beta). Gamma Decay http://ie.lbl.gov/education/glossary/AnimatedDecays/GammaDecay.html Additional animations: http://ie.lbl.gov/education/glossary/Glossary.htm

  47. ABSORPTION OF RADIATION

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