Tro Chemistry A Molecular Approach 37 Magic Numbers besides the NZ ratio the

Tro chemistry a molecular approach 37 magic numbers

This preview shows page 37 - 47 out of 95 pages.

Tro, Chemistry: A Molecular Approach 37 Magic Numbers besides the N/Z ratio, the actual numbers of protons and neutrons effects stability most stable nuclei have even numbers of protons and neutrons only a few have odd numbers of protons and neutrons if the total number of nucleons adds to a magic number, the nucleus is more stable same idea as the electrons in the noble gas resulting in a more stable electron configuration most stable when N or Z = 2, 8, 20, 28, 50, 82; or N = 126
Image of page 37
Tro, Chemistry: A Molecular Approach 38 Decay Series in nature, often one radioactive nuclide changes in another radioactive nuclide daughter nuclide is also radioactive all of the radioactive nuclides that are produced one after the other until a stable nuclide is made is called a decay series to determine the stable nuclide at the end of the series without writing it all out 1. count the number of and decays 2. from the mass no. subtract 4 for each decay 3. from the atomic no. subtract 2 for each decay and add 1 for each
Image of page 38
Tro, Chemistry: A Molecular Approach 39 U-238 Decay Series or or other combinations
Image of page 39
Tro's Introductory Chemistry, Chapter 17 40 Detecting Radioactivity To detect something, you need to identify what it does Radioactive rays can expose light-protected photographic film Use photographic film to detect its presence – film badges
Image of page 40
Tro's Introductory Chemistry, Chapter 17 41 Detecting Radioactivity Radioactive rays cause air to become ionized An electroscope detects radiation by its ability to penetrate the flask and ionize the air inside A Geiger-Müller Counter works by counting electrons generated when Ar gas atoms are ionized by radioactive rays
Image of page 41
42 Detecting Radioactivity Radioactive rays cause certain chemicals to give off a flash of light when they strike the chemical A scintillation counter is able to count the number of flashes per minute
Image of page 42
Tro, Chemistry: A Molecular Approach 43 Natural Radioactivity there are small amounts of radioactive minerals in the air, ground, and water even in the food you eat! the radiation you are exposed to from natural sources is called background radiation
Image of page 43
Tro, Chemistry: A Molecular Approach 44 Rate of Radioactivity it was discovered that the rate of change in the amount of radioactivity was constant and different for each radioactive “isotope” change in radioactivity measured with Geiger counter counts per minute each radionuclide had a particular length of time it required to lose half its radioactivity a constant half-life we know that processes with a constant half-life follow first order kinetic rate laws rate of change not affected by temperature means that radioactivity is not a chemical reaction!
Image of page 44
Tro, Chemistry: A Molecular Approach 45 Kinetics of Radioactive Decay Rate = k N N = number of radioactive nuclei t 1/2 = 0.693/ k the shorter the half-life, the more nuclei decay every second – we say the sample is hotter 0 t 0 t rate rate ln t N N ln k
Image of page 45
Tro, Chemistry: A Molecular Approach 46
Image of page 46
Image of page 47

You've reached the end of your free preview.

Want to read all 95 pages?

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture