Assignment #1
Read the contents below first, then answer question: Is there any mistake in the top table “Radioactive Decay and Nuclear Change” on Page 89 of Barron’s SAT book?
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Positron emission or beta plus decay (β+ decay) is a particular type of radioactive decay and a subtype of beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron . The positron is a type of beta particle (β+), the other beta particle being the electron (β–) emitted from the β– decay of a nucleus.
An example of positron emission (β+ decay) is shown with magnesium decaying into sodium:
23 23
12Mg → 11Na + β+
Because positron emission decreases proton number relative to neutron number, positron decay happens typically in large “proton-rich” radionuclides. Positron decay results in changing an atom of a chemical element into an atom of an element with an atomic number that is less by one unit.
Positron emission should not be confused with electron emission or beta minus decay (β– decay), which occurs when a neutron turns into a proton and the nucleus emits an electron.
Electron capture (sometimes called inverse beta decay) is also occasionally classified as a type of beta decay. (In some ways, electron capture can be regarded as the “opposite” of positron emission. It can only occur when electrons are available and requires less energy difference between parent and daughter, so occurs much more often in smaller atoms than positron emission does.)
In the process of electron capture, one of the orbital electrons, usually from the inner shell orbital, is captured by a proton in the nucleus, forming a neutron.
Reaction details:
p | + | e− | → | n |
Examples:
40 19K |
+ | e− | → | 40 18Ar |
Assignment #2
- Read “Decay Series, Transmutations and Half-life on Page 88, Barron’s SAT book,
- Read entire page 89 and 90.
- Then do Practice Excises #10 through #19 on page 92 and 93.