What is half-life and how is it calculated?
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.
What does it mean if a drug has a short half life?
Drugs or substances that have a shorter half-life tend to act very quickly, but their effects wear off rapidly, meaning that they usually need to be taken several times a day to have the same effect.
Why is a short half-life beneficial?
Doctors use radioactive isotopes as medical tracers. The nuclei must be active long enough to treat the condition, but they must also have a short enough half-life so that they don’t have time to injure healthy cells and organs.
Which half life is dangerous?
Depends what you mean by danger. Short half life isotopes like iodine-131 are dangerous with direct exposure. But with a half life of 8 days, it is 99% gone after a couple of months, and poses little long term environmental risk.
Which is more stable an isotope with a short half life or one with a long half life?
1 Answer. Stefan V. The longer the half-life, the more stable the nuclide.
How do you know if an isotope is stable?
The principal factor for determining whether a nucleus is stable is the neutron to proton ratio. Elements with (Z<20) are lighter and these elements’ nuclei and have a ratio of 1:1 and prefer to have the same amount of protons and neutrons. Carbon has three isotopes that scientists commonly used: C12, C13, C14.
What percent of a sample remains after one half-life?
As you can see from this table, the amount of reactant left after n half-lives of a first-order reaction is (1/2) n times the initial concentration….Half-Lives.
| Number of Half-Lives | Percentage of Reactant Remaining | |
|---|---|---|
| 1 | 100%2=50% | 12(100%)=50% |
| 2 | 50%2=25% | 12(12)(100%)=25% |
| 3 | 25%2=12.5% | 12(12)(12)(100%)=12.5% |
| n | 100%2n | (12)n(100%)=(12)n% |
What is a stable element?
An atom is stable if the forces among the particles that makeup the nucleus are balanced. An atom is unstable (radioactive) if these forces are unbalanced; if the nucleus has an excess of internal energy. Instability of an atom’s nucleus may result from an excess of either neutrons or protons.