1. NUCLEAR CHEMISTRY

2. Discovery of Radiation Roentgen (1895) Discovered a mysterious form of radiation was given off even without electron beam. This radiation could pass through paper and other objects but not dense materials (lead, bone). Called them X-rays Studied fluorescent materials that glowed when hit with a beam of electrons.

3. Becquerel (1896) Studied fluorescent minerals containing uranium. Discovered radioactivity occurs in unstable atoms. Thought that an external source was needed to produce the mysterious radiation. Found that uranium emits radiation without external source.

4. Thought radioactivity was a property of only heavy elements. Pierre and Marie Curie During study, discovered new radioactive elements: Polonium and Radium. Wondered how small mass can give off large amount of energy: Explained by Einstein with E=mc 2.

5. Studied radioactivity and named types of nuclear radiation. Rutherford Discovered that elements decay into other elements after emitting nuclear radiation. Called it Nuclear Decay. Gold foil experiment revealed that the mass of an atom is concentrated in the nucleus (atom is mostly space)

6. Atomic Structure Recall: Atoms – consist of a positively charged nucleus, which has protons and neutrons. IsotopeSymbol# protons# neutronsAtomic Mass Mo-101 H-2 C-14 U-238 Bi-210 He-4 42 1 6 92 83 2 59 1 8 146 127 2 101 2 14 238 210 4 Isotope – atoms of the same chemical element that have a different number of neutrons. Each isotope of a given element is designated by the total number of its protons plus its neutrons.

7. Alpha Emission parent nuclide daughter nuclide alpha particle Numbers must balance!! Occurs when the nucleus has too many protons & neutrons which causes instability. 2 protons & 2 neutrons emitted.

8. Alpha Emission Ex. Plutonium-239 undergoes alpha decay + 239 Atomic Mass: = 2354 + 94 Atomic #: = 92 2 + Masses must be equal = Conservation of mass

9. Ex. Polonium-210 undergoes alpha decay to produce this daughter nuclide + Alpha Emission Atomic Mass: 210 = A4 + Atomic #: 84 = Z 2 + 210 = A4 - = 206 84 = Z2 - = 82 =

10. Beta Emission electron Occurs when there’s too many neutrons in nucleus. A neutron is converted into a proton & an electron. Electron is then emitted.

11. Ex. Polonium-210 undergoes beta decay to produce this daughter nuclide + Beta Emission Atomic Mass: 210 = A0 + Atomic #: 84 = Z + 210 = A0 - = 84 = Z1 + = 85 =

12. positron Positron Emission Occurs when there’s too many protons in nucleus. Proton is converted into a neutron and a positron. Positron is then emitted.

13. Ex. Polonium-210 undergoes positron emission to produce this daughter nuclide + Positron Emission Atomic Mass: 210 = A0 + Atomic #: 84 = Z +1 + 210 = A0 - = 84 = Z1 - = 83 =

14. Electron Capture electron Occurs when there’s too many protons in nucleus. An inner orbital electron is “captured”. Proton & electron combines to form a neutron.

15. Ex. Polonium-210 captures an electron to produce this daughter nuclide + Electron Capture Atomic Mass: 210 = A0 + Atomic #: 84 = Z + A = 210 Z = 83 =

16. Gamma Emission Emission of high energy changed the nucleus from an excited state to a ground state. High energy wave emitted from the nucleus of an unstable atom.

17. Ex. Polonium-210 undergoes gamma decay to produce this daughter nuclide + Gamma Emission Atomic Mass: 210 = A0 + Atomic #: 84 = Z 0 + A = 210 Z = 84 =

18. Nuclear Decay Why nuclides decay –need stable ratio of neutrons to protons Transmutation- One element becomes another. More than 83 protons means that the nuclei is unstable (radioactive)

19. Types of Radiation Alpha particle (  ) –helium nucleus paper 2+ Beta particle (  -) –electron 1- lead Positron (  +) –positron 1+ Gamma (  ) –high-energy photon 0 concrete ChargeShielding

21. Penetrating Ability of Radiation