Nuclear Chemistry

Types of Radioactive DecayKinetics of Decay

Nuclear Transmutations

Remember the Nucleus

• Remember that the nucleus is comprised of the two nucleons, protons and neutrons.

• The number of protons is the atomic number.• The number of protons and neutrons together is

effectively the mass of the atom.

Isotopes

• Not all atoms of the same element have the same mass due to different numbers of neutrons in those atoms.

• There are, for example, three naturally occurring isotopes of uranium:– Uranium-234– Uranium-235– Uranium-238

Radioactivity: Kinetic Stability• It is common for some nuclides of an element

to be unstable, or radioactive.• We refer to these as radionuclides.• They can spontaneously decay emitting

electromagnetic radiation and particles .

Types ofRadioactive Decay

Alpha DecayAlpha decay is the loss of an -particle (a helium nucleus), results in more stable iosotope.

He42

U23892 U234

90 He42+

-particle =

Beta DecayBeta decay is the loss of a -particle (a high energy electron).

0

−1 e0−1or

I13153 Xe131

54 + e0−1

Positron EmissionSome nuclei decay by emitting a positron, a particle that has the same mass as but opposite charge to that of an electron.

e01

C116 B11

5 + e01

Gamma EmissionThis is the loss of a -ray, which is high-energy radiation that almost always accompanies the loss of a nuclear particle.

00

Electron Capture (K-Capture) p. 878

Addition of an electron to a proton in the nucleus is known as electron capture or K-capture. – The result of this process is that a proton is

transformed into a neutron.

p11 + e0

−1 n10

Summary Table 21.3 p. 879