1. Nuclear Chemistry

2. Definitions
Nuclear radiation: radiation emitted from a nucleus during nuclear decay
alpha particle (a): a helium nucleus, He2+; contains two protons and two neutrons, has mass of 4 amu, and atomic number 2
beta particle (b): an electron; has a charge of -1, and a mass of amu
positron (b+): has the mass of an electron but a charge of +1
gamma ray (g): high-energy electromagnetic radiation

3. Electromagnetic Radiation
All electromagnetic radiation consists of waves
the wavelength, l is the distance between each crest.
frequency, n: the number of crests that pass a given point in a second

4. Electromagnetic Radiation
The electromagnetic spectrum

5. Nuclear Radiation
Table 9.1 summarizes the types of nuclear radiation we deal with in this chapter

6. Nuclear Radiation There are more than 300 naturally occurring isotopes
of these 264 are stable, they do not give off radiation
among the lighter elements, stable isotopes have approximately the same number of protons and neutrons; this is the case of 126C, 168O, and 2010Ne
among the heavier elements,stability requires more neutrons than protons
More than 1000 artificial isotopes have been made in the laboratory; all are radioactive

7. Beta Emission
beta emission: a type of nuclear decay in which a neutron is converted to a proton and an electron, and the electron is emitted from the nucleus
emission of a beta particle transforms the element into a new element with the same mass number but an atomic number one unit greater
phosphorus-32, for example, is a beta emitter
note in this nuclear decay equation that the sum of both the mass numbers and atomic numbers are the same on each side of the equation

8. Beta Emission
Problem: carbon-14 is a beta emitter. When it undergoes beta emission, into what element is it converted?

9. Beta Emission
Problem: carbon-14 is a beta emitter. When it undergoes beta emission, into what element is it converted?
Solution: it is converted into nitrogen-14

10. Alpha Emission
alpha emission: a type of nuclear decay in which a helium nucleus is emitted from the nucleus
in alpha emission, the new element formed has an atomic number two units lower and a mass number four units lower

11. Positron Emission
positron emission: a type of nuclear decay in which a positive electron is emitted from the nucleus
in positron emission, the new element formed has an atomic number one unit lower but the same mass number

12. Gamma Emission
In pure gamma emission, there is no change in either the atomic number or the mass number of the element
a nucleus in a higher-energy state emits gamma radiation as it returns to its ground state (its most stable energy state)
in this example, the notation “11m” indicates that the nucleus of boron-11 is in a higher-energy (excited) state

13. Half-Life
half-life of a radioisotope, t1/2: the time it takes one half of a sample of a radioisotope to decay
iodine-131 decays by beta, gamma emission

15. Characteristics of Radiation
Intensity
to measure intensity, we take advantage of the ionizing property of radiation
instruments such as a Geiger-Müller or proportional counter contain a gas such as helium or argon
when a radioactive nucleus emits beta particles, these particles ionize the gas in the instrument; it registers the ionization by indicating that an electric current has passed between two electrodes
another measuring device, called a scintillation counter, has a phosphor that emits a unit of light when a beta particle or gamma ray strikes it
intensity is recorded in counts/min or counts/s

16. Characteristics of Radiation
Energy and penetrating power

17. Radiation Dosimetry
average exposure to radiation from common sources

18. Nuclear Medicine
Radioisotopes have two main uses in medicine; diagnosis and therapy

19. Nuclear Medicine

20. Nuclear Fusion
The transmutation of two hydrogen nuclei into a helium nucleus liberates energy in the form of photons
this process is called nuclear fusion
all transuranium elements (elements with atomic number greater than 92) are artificial and have been prepared by nuclear fusion
to prepare them, heavy nuclei are bombarded with lighter ones

21. Nuclear Fusion examples are the preparation of Bk, Cf, and Lr
these transuranium elements are unstable and have very short half-lives; that of lawrencium-257, for example, is only 0.65 second

22. Nuclear Fission
Nuclear fission: the fragmentation of larger nuclei into smaller ones
when uranium-235 is bombarded with neutrons, it is broken into two smaller elements
more importantly, energy is released because the products have less mass than the starting materials
the mass decrease in fission is converted into energy
this form of energy is called atomic energy

23. Nuclear Fission
Nuclear fission is a chain reaction

24. Nuclear Fission
today more than 15% of the electrical energy in the United States is supplied by nuclear power plants
disposal of spent but still radioactive fuel materials is a major long-term problem
spent fuel contains high-level fission products together with recoverable uranium and plutonium
in addition, there are radioactive wastes from nuclear weapons programs, research reactors, and so forth
recently the government gave its final approval to store nuclear wastes at a site deep under Yucca Mountain in Nevada