1 Nuclear Chemistry

2 Radioactivity Emission of subatomic particles or high- energy electromagnetic radiation by nuclei Emission of subatomic particles or high- energy electromagnetic radiation by nuclei Such atoms/isotopes said to be radioactive Such atoms/isotopes said to be radioactive

3 Its discovery Discovered in 1896 by Becquerel Discovered in 1896 by Becquerel Called strange, new emission uranic rays Called strange, new emission uranic rays Cuz emitted from uranium Cuz emitted from uranium Marie Curie & hubby discovered two new elements, both of which emitted uranic rays Marie Curie & hubby discovered two new elements, both of which emitted uranic rays Polonium & Radium Polonium & Radium Uranic rays became radioactivity Uranic rays became radioactivity

4 Types of radioactivity Rutherford and Curie found that emissions produced by nuclei Rutherford and Curie found that emissions produced by nuclei Different types: Different types: Alpha decay Alpha decay Beta decay Beta decay Gamma ray emission Gamma ray emission

5 Isotopic symbolism Let ’ s briefly go over it Let ’ s briefly go over it Proton = 1 1 p Proton = 1 1 p Neutron = 1 0 n Neutron = 1 0 n Electron = 0 -1 e Electron = 0 -1 e

6 Types of decay: alpha decay Alpha (  ) particle: helium-4 bereft of 2e - Alpha (  ) particle: helium-4 bereft of 2e - = 4 2 He = 4 2 He Parent nuclide  daughter nuclide + He-4 Parent nuclide  daughter nuclide + He U  Th He Daughter nuclide = parent nuclide atomic # minus 2 Daughter nuclide = parent nuclide atomic # minus 2 Sum of atomic # ’ s & mass # ’ s must be = on both sides of nuclear equation! Sum of atomic # ’ s & mass # ’ s must be = on both sides of nuclear equation!

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8 Alpha decay Has largest ionizing power Has largest ionizing power = ability to ionize molecules & atoms due to largeness of  -particle = ability to ionize molecules & atoms due to largeness of  -particle But has lowest penetrating power But has lowest penetrating power = ability to penetrate matter = ability to penetrate matter Skin, even air, protect against  -particle radiation Skin, even air, protect against  -particle radiation

9 Beta decay Beta (  ) particle = e - Beta (  ) particle = e - How does nucleus emit an e - ? How does nucleus emit an e - ?  neutron changes into proton & emits e -  neutron changes into proton & emits e -  1 0 n  1 1 p e  1 0 n  1 1 p e Daughter nuclide = parent nuclide atomic number plus 1 Daughter nuclide = parent nuclide atomic number plus Cs  Ba e -

10 Beta decay Lower ionizing power than alpha particle Lower ionizing power than alpha particle But higher penetration power But higher penetration power Requires sheet of metal or thick piece of wood to arrest penetration Requires sheet of metal or thick piece of wood to arrest penetration  more damage outside of body, but less in (alpha particle is opposite)  more damage outside of body, but less in (alpha particle is opposite)

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12 Gamma ray emission Electromagnetic radiation Electromagnetic radiation High-energy photons High-energy photons 0 0  0 0  No charge, no mass No charge, no mass Usually emitted in conjunction with other radiation types Usually emitted in conjunction with other radiation types Lowest ionizing power, highest penetrating power  requires several inches lead shielding Lowest ionizing power, highest penetrating power  requires several inches lead shielding

13 Problems Write a nuclear equation for each of the following: Write a nuclear equation for each of the following: 1. beta decay in Bk alpha decay of Ra-224