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Isotopes, Half Lives and Neutron Activation

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Please see the following posting for questions regarding isotopes, half-lives and neutron activation. See attached file.

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1. Chemical properties of an element are largely decided by the electrons revolving around the nucleus. In any chemical reaction it is the electrons in the outermost orbit of the atom which play the major role (such as forming bonds to form compounds). The nucleus comprising the protons and neutrons does not play any significant role in chemical reactions but it defines the physical properties of the element viz. strength, ductility, melting point etc.

Different isotopes of the same element have same number of electrons revolving around their nucleus (and same number of protons in their nuclei) but different number of neutrons in their nuclei. Hence, chemical properties of the isotopes are same but their physical properties vary.

4. The force that holds the nucleus together despite presence of positively charged protons (by overcoming the strong electrostatic repulsion between them) is known as "Strong nuclear force". This force acts at extremely short range (of the order of half the diameter of a proton or neutron). Hence, this ...

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Isotopes, half lives and neutron activation are examined in the following solution.

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Problems About Radioactivity and Nuclear Chemistry

1. At 8:00 a.m., a patient receives a 58-mg dose of I -131 to obtain an image of her thyroid. If the nuclide has a half-life of 8 days, what mass of the nuclide remains in the patient at 5:00 p.m. the next day? (Assume no excretion of the nuclide from the body).
Express your answer using two significant figures.

2. A radioactive sample contains 1.55g of an isotope with a half-life of 3.8 days. What mass of the isotope will remain after 5.5 days? (Assume no excretion of the nuclide from the body.) Express your answer using two significant figures.

3. A particular smoke detector contains 1.45μCi of 241 Am, with a half-life of 458 years. The isotope is encased in a thin aluminum container. Calculate the mass of 241 Am in grams in the detector. Express your answer numerically in grams.

4. The following conversion factors may help you when working this problem:
Activity in becquerels (Bq ) = activity in disintegrations per second (dps).

1.00 mCi=3.70×10 7 Bq. Neutron activation analysis for a sample of a rock revealed the presence of 59 26 Fe, which has a half-life of 46.3days. Assuming the isotope was freshly separated from its decay products, what is the mass of 59 26 Fe in a sample emitting 1.00 mCi of radiation? Express your answer in grams to three significant figures.

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