To define half-life. To determine the lot of radioactive substance continuing to be after a given number of half-lives.

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Whether or no a offered isotope is radioactive is a characteristics of that details isotope. Part isotopes are stable indefinitely, while others are radioactive and decay with a characteristic form of emission. Together time passes, less and less of the radiation isotope will certainly be present, and the level of radioactivity decreases. One interesting and also useful element of radioactive degeneration is the half-life. The half-life the a radioactive isotope is the amount of time the takes for one-half the the radiation isotope to decay. The half-life the a specific radioactive isotope is constant; that is unaffected by conditions and is live independence of the initial lot of that isotope.

Consider the complying with example. Expect we have actually 100.0 g the 3H (tritium, a radiation isotope the hydrogen). It has actually a half-life the 12.3 y. After ~ 12.3 y, half of the sample will have actually decayed to 3He by create a beta particle, so that just 50.0 g the the original 3H remains. After one more 12.3 y—making a total of 24.6 y—another fifty percent of the remaining 3H will have actually decayed, leave 25.0 g that 3H. After an additional 12.3 y—now a total of 36.9 y—another half of the staying 3H will have decayed, leaving 12.5 g the 3H. This sequence of events is illustrated in figure (PageIndex1).

Exercise (PageIndex2)

A sample of (ceAc)-225 originally consisted of 80 grams and after 50 days just 2.5 grams the the initial (ceAc)-225 remain. What is the fifty percent life of (ceAc)-225?