Question:
Half life
1) Radioisotopes such as aluminum -26, which is believed to have been present in the solar system when earth was formed but can no longer be detected, are known as extinct radionuclides. The half-life for the decay of aluminum -26 is 7.20 x 10 ^5 years.
2) How many years did it take for 99.99% of the aluminum -26 to decay? If Earth was formed 4.6 x10^9 years ago, what percentage of the aluminum-26 present when the solar system was formed is still present today?