Ch 21 Nuclear Chemistry The Nucleus n Protons

Ch. 21 Nuclear Chemistry

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

The Nucleus ________: the difference between the mass of an atom and the sum of the masses of its protons, neutrons and electrons. n _________: the energy released when a nucleus is formed from nucleons. n __________: nucleons exist in different energy levels, or shells, in the nucleus. The numbers of nucleons that represent completed nuclear energy levels ~ 2, 8, 20, 28, 50, 82 and 126 are called Magic Numbers. n 21 -3

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

Radioactive Decay 21 -5

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

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

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

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

Radioactive Decay _______ (γ): high energy electromagnetic waves emitted from a nucleus as it changes from an excited state to a ground state. n Example: Balance the following reaction: 212 Po → 4 He + ____ 84 2 Po → 42 He + 20882 Pb 1) Balance the following reaction: 253 Es + 4 He → 1 n + ____ 99 2 0 212 253 84 99 Es + 42 He → 10 n + 256101 Md 21 -10

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

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

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

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

Ch. 21 The End!