Nuclear Transformations

Nuclear Stability and Decay Band of stability – A region where the neutron-to-proton ratio stabilizes the nucleus. The neutron-to-proton ratio determines the type of decay that occurs. Positron (0+1e or β+) – a particle with the mass on an electron but holds a positive charge.

Half-Life Half-life (t1/2) – the time required for one half of the nuclei of a radioisotope sample to decay to products. After each half-life, half of the existing radioactive atoms have decayed into atoms of new elements. Half-lives can be as short as a fraction of a second or as long as billions of years.

This slide is an FYI Since Carbon-14 has a half-life of 5715 years, researchers use a method called carbon dating by comparing the decay of carbon-14 to other, more stable forms of carbon. This gives the researchers an estimate the age of a once living organism.

Using Half-Life Calculations Carbon-14 emits beta radiation and decays with a half-life (t1/2) of 5715 years. Assume you start with a mass of 2.00X10-12 g of carbon-14. a.) How long is three half-lives? 17,145 years b.) How many grams of the isotope remain at the end of three half-lives? 2.50X10-13g

Let’s Try Another Manganese-56 is a beta emitter with a half-life of 2.6 h. What is the mass of manganese-56 in a 1.0 mg sample of the isotope at the end of 10.4 h? Half-Life Time Amount ____ 0 half-lives 0 hrs 1.00 mg 1 half-life 2.6 hrs 0.50 mg 2 half-lives 5.2 hrs 0.25 mg 3 half-lives 7.8 hrs 0.125 mg 4 half-lives 10.4 hrs 0.063 mg Mn-56

Transmutation Reactions Transmutation – the conversion of an atom of one element to an atom of another element. Transmutation can occur: by radioactive decay. (Natural) when particles bombard the nucleus of an atom. (Artificial) Transuranium elements – elements with atomic numbers above 92 on the periodic table. None of these elements occur in nature.

Apply What You’ve Learned Complete and balance the equations for the following nuclear reaction: 2713Al + 42He ----> 3014Si + ? 11H or 11P A radioisotope has a half-life of 4 days. How much of a 20 g sample of this isotope remains at the end of 4 days? 10 g

25.2 pg. 886 #'s 14, 15, 16 Read 25.3-25.4 pgs. 888-897