Ch. 21 Nuclear Chemistry

Cl The Nucleus Nucleons: Protons and neutrons. Nuclide: an atom, identified by the number of protons and neutrons in its nucleus. Nuclides can be written with the name or symbol, followed by a dash with the mass number: Chlorine-35 or Cl-35, or as follows: 21-2 Cl Atomic mass = 35 17 Atomic number =

The Nucleus Mass Defect: the difference between the mass of an atom and the sum of the masses of its protons, neutrons and electrons. Nuclear Binding Energy: the energy released when a nucleus is formed from nucleons. Nuclear Shell Model: nucleons exist in different energy levels, or shells, in the nucleus. 21-3

Radioactive Decay Nuclear Reaction: a reaction that changes the nucleus of an atom. Transmutation: a change in the identity of a nucleus as a result of a change in the number of its protons. Nuclear Particles Type Symbol Charge Alpha particle 42He +2 Beta particle 0-1β -1 Positron 0+1β +1 Neutron 10n 0 Gamma Ray γ 0 21-4

Radioactive Decay 21-5

Radioactive Decay Radioactive Decay: the spontaneous disintegration of a nucleus into a slightly lighter nucleus, accompanied by emission of particles, electromagnetic radiation or both. Nuclear Radiation: particles or electromagnetic radiation emitted from the nucleus during radioactive decay. Radioactive Nuclide: an unstable nucleus that undergoes radioactive decay. 21-6

Radioactive Decay Alpha emission (α): two protons and two neutrons bound together, emitted during some types of radioactive decay. 21-7

Radioactive Decay Beta emission (β): an electron emitted from the nucleus during some types of radioactive decay. 21-8

Radioactive Decay Positron emission : a particle that has the same mass as an electron, but has a positive charge and is emitted during some types of radioactive decay. 21-9

Radioactive Decay Gamma Rays (γ): high energy electromagnetic waves emitted from a nucleus as it changes from an excited state to a ground state. Example: Balance the following reaction: 21284 Po → 42He + ________ 21284 Po → 42He + 20882 Pb 1) Balance the following reaction: 25399 Es + 42He → 10n + ________ 25399 Es + 42He → 10n + 256101 Md 21-10

Radioactive Decay Half-Life : the time required for half the atoms of a radioactive nuclide to decay. 21-11

Radioactive Decay Decay Series: a series of radioactive nuclide produced by successive radioactive decay until a stable nuclide is reached. 21-15

Radioactive Decay Nuclear Fission: a very heavy nucleus splits into more stable nuclei of intermediate mass, starting a chain rxn. 21-13

Radioactive Decay Nuclear Fusion: low mass nuclei combine to form a heavier, more stable nucleus. 21-14

Ch. 21 The End!