Radioactive Decay Nuclear Reactions Transmutation and Decay Series

Radioactive Decay & Nuclear Reactions Transmutation and Decay Series Fission and Fusion

Radioactive Decay • When a radioactive isotope decays, it emits one of three forms of radiation: – alpha particle α • 4 He nucleus • 2+ charge – beta particle source • e- (electron) • 1 - charge – gamma ray • High frequency form of electromagnetic radiation (I. e. light) • No charge γ β

Alpha, Beta, and Gamma Radiation please write this on the back of pg. 4

Transmutation • When one atom turns into another sort of atom (called a daughter atom), it is called transmutation. • When different forms of radiation are emitted, different changes occur: – Alpha emission: Loss of 2 protons and neutrons, therefore atomic mass is less by 4. – Beta emission: Loss of an electron from the nucleus, therefore gain of a proton. (n 0 = p+ + e-, but only in nuclear reactions) – Gamma emission: No transmutation.

A Few Definitions • Daughter Atom -The atom produced in a transmutation. • Half-Life -- The amount of time it takes for half of a radioactive substance to decay into daughter atoms.

The Decay Series of Uranium-238 • The following table and diagram for uranium-238 show its transmutation. As it undergoes radioactive decay, a chain of products is formed as a result of one by-product itself decaying to another element, which in turn decays further until finally reaching an element that is stable. In this case that stable element is Lead. • So: – 238 U 234 Th 234 Pa 234 U many more 206 Pb (stable!)

The Decay Series of Uranium-238

Fission and Fusion • Fission: – The splitting of the nucleus of an atom into fragments. • An atom must have sufficient mass for a fission chain reaction: critical mass. • Examples: A-bomb, nuclear reactors • Fusion: – The combining of two or more atomic nuclei. • Examples: H-bomb, the sun, nuclear research.

Fusion Examples • Fusion occurs in the sun, with hydrogen combining to make helium, but also with larger atoms:

“Why does the sun shine? ” • Here is a song performed by They Might Be Giants, called “Why Does the Sun Shine? ” SING ALONG -- Chorus: The sun is a mass of incandescent gas, a gigantic nuclear furnace Where hydrogen is changed into helium at a temperature of millions of degrees.