# U pb dating half life

The table below illustrates half-lives for selected elements.In addition, the final elemental product is listed after the decal process.Each radioactive isotope will have its own unique half-life that is independent of any of these factors.Figure $$\Page Index$$: For cobalt-60, which has a half-life of 5.27 years, 50% remains after 5.27 years (one half-life), 25% remains after 10.54 years (two half-lives), 12.5% remains after 15.81 years (three half-lives), and so on. The half-lives of many radioactive isotopes have been determined and they have been found to range from extremely long half-lives of 10 billion years to extremely short half-lives of fractions of a second.A useful concept is half-life (symbol is $$t_$$), which is the time required for half of the starting material to change or decay.
After 720 hours, how much of the original $$\ce$$-225 remains? Solution To determine the number of half-lives (n), both time units must be the same.
$720\cancel\times \dfrac= 30\, days$ $n=3 =\dfrac$ $\text = \dfrac (8.0 \, ug)$ After 720 hours, 1.0 ug of the material remains as $$\ce$$-225 .