Table of Contents
- 1 Does a shorter half-life mean more unstable?
- 2 Do half lives ever reach zero?
- 3 Why are half-lives different?
- 4 How are half lives determined?
- 5 What is the difference between half-life and biological half-life?
- 6 What makes a nucleus a stable or an unstable nucleus?
- 7 What’s the difference between a short half life and a long half life?
Does a shorter half-life mean more unstable?
A short half-life, on the other hand, implies that the radioactive substance decays to half of its initial mass very quickly. This means that it will be very unstable, since it will decay almost completely in a much shorter time.
Do unstable substances have a half-life?
Yes, the decay half-life of a radioactive material can be changed. Radioactive decay happens when an unstable atomic nucleus spontaneously changes to a lower-energy state and spits out a bit of radiation. This process changes the atom to a different element or a different isotope.
Do half lives ever reach zero?
Regardless of which variable or version of the equation you use, the function is a negative exponential, meaning it will never reach zero. For each half-life that passes, the number of nuclei is halved, becoming smaller and smaller but never quite vanishing – at least, this is what happens mathematically.
Why do radioisotopes have short half lives?
How are radioisotopes used? Some radioisotopes used in nuclear medicine have short half-lives, which means they decay quickly and are suitable for diagnostic purposes; others with longer half-lives take more time to decay, which makes them suitable for therapeutic purposes.
Why are half-lives different?
Here are the top questions that students are asking Flexi for this concept: If there is 50% uranium-235 remaining in a sample, about how old is it? The half life of uranium-235 is about 700 million years. Therefore, if a sample has 50% of the original isotope remaining, the sample is about 700 million years old.
What has a short half-life?
Hydrogen-7 ( about 23x10E-24) has the shortest half life.
How are half lives determined?
The half-life is then determined from the fundamental definition of activity as the product of the radionuclide decay constant, λ, and the number of radioactive atoms present, N. One solves for λ and gets the half-life from the relationship λ = ln2/T1/2.
Why does a half-life graph never reach zero?
The half-life is plotted as a red point. One funny property of exponential decay is that the total mass of radioactive isotopes never actually reaches zero. The mass just keeps getting closer and closer to zero as the amount of time for the isotope to decay gets larger and larger.
What is the difference between half-life and biological half-life?
However, there are different types of half-lives that describe different things. The 30 years is the physical half-life. Here are the different half-life measures and what they mean….Half Lives.
| Isotope | Physical Half-Life | Biological Half-Life |
|---|---|---|
| Cs-134 | 2 years | 70 days |
| Iodine-131 (I-131) | 8.1 days | 138 days |
| Sr-90 | 28 years | 18,000 days |
What happens to the number of nuclei in a half life?
In one half-life t1/2, the number decreases to half of its original value. Half of what remains decay in the next half-life, and half of those in the next, and so on. This is an exponential decay, as seen in the graph of the number of nuclei present as a function of time.
What makes a nucleus a stable or an unstable nucleus?
There are only certain combinations of neutrons and protons, which forms stable nuclei. If there are too many or too few neutrons for a given number of protons, the resulting nucleus is not stable and it undergoes radioactive decay. Unstable isotopes decay through various radioactive decay pathways.
What happens when a radioactive substance has a short half life?
A short half-life, on the other hand, implies that the radioactive substance decays to half of its initial mass very quickly. Moreover, after another half-life passes, it decays to half of its current mass again. Another half-life passes, and its mass gets halved again. This means that it will be very unstable,…
What’s the difference between a short half life and a long half life?
You can expect it to be around for a long period of time. A short half-life, on the other hand, implies that the radioactive substance decays to half of its initial mass very quickly.