Chapter 21 Worksheet #1 Name ___________ The symbol for a nuclide has the form: •;;Au The superscript (197) indicates the number of nucleons (the sum of the protons+ neutrons) The subscript (79) indicates the charge on the nucleus (the number of protons for a nuclide). In the case of subatomic particles, the subscript still indicates the charge but will not correspond to the number of protons. For example, a beta particle has the symbol -~ P indicating it has no nucleons and a charge of -1. A beta particle is an _____ ejected from a nucleus. Write symbols for: (1) an alpha particle (same as a helium nucleus) ___ or ____ (2) a positron ( a positive electron) ___ or ____ (3) aneutron ____ (4) iron-59 ___ (5) uranium-235 ____ A nuclear process will have a form similar to that shown below: E F G H Balancing nuclear equations: (1) the number of nucleons are conserved ( A+B = C+D) (2) nuclear charge is conserved ( E+F = G+H ) For natural radioactivity, there is usually only one symbol on the left side of the equation (the exception is electron capture). There are four primary types of natural radioactivity. Alpha decay results in emission of an alpha particle and causes the nucleus to decrease its mass number by 4 and its atomic number by 2. Beta decay has the net effect of converting a neutron in the nucleus to a proton. Positron emission converts a proton into a neutron. Electron capture occurs when an electron from the electron cloud gets pulled into the nucleus and converts a proton into a neutron. Write balanced equations for the following natural radioactivity processes: Alpha Decay of 2~U Beta Decay of :~co Positron Emission of •: F Electron Capture of 1~!W Write balanced equations for the following hwnan-induced nuclear processes: . 180 ]H 1 Nuclear Transmutation: 8 +1 + __ Neutron capture: ]JCo+~n __+ r (called a capture gamma) 235U+ + y Fission (2 step process): 92 0 92 +201n 92 56 + ___ We classify nuclei according to the parity of the neutron to proton ratio. For example, ii Na is classified as even/odd since it has an even number of neutrons and an odd number of protons. h°a• Z.I. I The stability of nuclides depends upon their neutron to proton ratio. Figure~ your text J a {ial8t 9H) indicates the relationship between nonradioactive (stable) nuclides and their neutron f • -, T) to proton ratios. The region which encompasses all the nonradioactive nuclides is called the "Belt of Stability." The five rules listed below are useful for predicting the stability of a nuclide; i.e., the nuclides which fall within the Belt of Stability: 1. Nonradioactive always have at least as many neutrons as protons (2 exceptions: 1H and 3He). 2. For an odd/even or even/odd nucleus, if tile mass number of the nud~ is different by more than 1 amu from the rounded atomic mass of the element taken from the periodic tab~ then the nuclide is radioactive. 3. For an even/even nucleus, if the mass number of the nuclide is different by more than 3 amu from the rounded atomic mass of the element taken from the periodic table, then the nuclide is radioactive. 4. For odd/odd nuclei only four stable isotopes are nonradioactive: 2H, 6Li, 18B and 14N. All others are radioactive. 5. All nuclides with Z>83 are radioactive. Rules for determining the type of radioactivity for a radioactive nuclide: 1. If the number is greater than the mass number found on the periodic table, then the nuclide will decay by beta emission. 2. If the mus number is less than the- mass number found on the periodic table, then the nuclide will either positron emit (for light nuclei) or electron capture (for heavy nuclei). 3. Nuclides with Z>83 tend to alpha emit. Predict whether the following nuclides are radioactive. If radioactive, predict how it would decay. a. 240Pu 94 189,: C. 11 .1.r e. f¢ct g. ::Nb .