Download Ch3 Video 2 pdf file

ch3Video2.notebook
December 19, 2014
Chapter 3 Video 2: Radioactivity
Objectives:
• be familiar with the terminology of radioactive decay
• be able to write the nuclear symbol and charge for alpha and beta particles
• be able to describe gamma decay
• be able to compare the penetrating ability of alpha, beta and gamma radiation
• be able to state the effects of alpha, beta and gamma decay on the nucleus of a radioactive atom
• be able to state the definition of half­life of a radioactive atom
Dec 17­3:36 PM
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ch3Video2.notebook
December 19, 2014
Radioactivity discovered
Henri Becquerel
Pierre & Marie Curie
Radioactive Decay -• the spontaneous emission of energy and usually
particles from an unstable nucleus to produce a
more stable atom
• when particles are emitted, the identity of the
element changes. (transmutation)
Daughter nuclide = new atom that is the result of a
nuclear transmutation
Jan 6­8:23 AM
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December 19, 2014
Experimental determination of the nature of radioactivity
Dec 17­1:16 PM
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ch3Video2.notebook
December 19, 2014
3 Types of Radioactive Decay
Alpha Decay = emission of an alpha particle from the atom's nucleus
Alpha Particle = a Helium nucleus
Nuclear Symbol = Daughter nuclide is a different, lighter element (mass# decreases by 4)
Beta Decay = emission of a beta particle from the atom's nucleus
Beta Particle = an electron
Nuclear Symbol = In the nucleus, a neutron becomes a proton and ejects an electron
Daughter nuclide has the same mass, but one less neutron
Gamma decay ­­ a highly energized nucleus emits energy (electromagnetic radiation, which is high energy light) to become more stable
The Daughter nuclide is the same atom as the Parent
There is no nuclear symbol for Gamma because it is NOT a particle, just energy. It is abbreviated using the Greek letter gamma = We will use the nuclear symbols for alpha and beta particles to
write nuclear decay equations next class. Be sure you can write
each of those symbols correctly.
Jan 6­8:23 AM
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beta decay
Jan 5­10:31 AM
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Half-life = t1/2 = the time for one half of a radioactive
sample to decay and transmutate into a new, more
stable atom
Example: if t1/2 is 1 day, after 1 day, a sample of 1000 atoms will have transmutated,
leaving only 500 atoms of the original isotope. After 2 days (2 half-lives), only 250 of
the original isotopes will remain unchanged.
Question: What fraction of the original sample remains unchanged after 4 half-lives?
Jan 6­1:49 PM
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