I assume you mean "half life". That means, how long does it take for half of the atoms in a sample to decay.
It is 2.6 years.
One-half of the original amount. That's precisely the definition of "half-life".
It is 100 years.
The length of time it takes for half of a radioactive sample to decay
1 / 26 = 1 / 64.
It depends on the radioisotope. They do not all have the same half life.
That would be "half-life". That means, how long does it take for half of the atoms in a sample to decay (convert into some other type of atom). Depending on the specific isotope, this "half-life" can be anything from a tiny fraction of a second, to billions of years.
It is 432 years.
It is 2.6 years.
It is 15.02 hours.
It is 14.6 years.
It is 300,000 years.
It is 5.27 years.
It is 18.11 years.
It is 14.1 hours.
It is 11.2 years.
It is 252 days.