3
At the end of the first half life, there will theoretically be 50% remaining.
2 half lives: 25%
3 half lives:12.5 %
scientists can determine the age of somthing by finding out how much carbin 14 there is left in the sample. the reason fro using carbon 14 is because it has a very predictable half life of 5730(plus or minus 40) years. half life is the decay rate of certain materials. by knowing the begging amount of carbon 14 present in the sample they can determine by the amount left how old it is.this is a pretty easy subject to look up if you have any pther questions.
literally - "left behind". In chemistry - usually refers to what doesn't evaporate from a sample left at room temperature for a long time, or if the sample is heated to another specific temperature (like in fractional distillation). Elements and compounds that have low boiling points tend to evaporate quickly, higher boiling points take longer and require more heat, so they get left behind. Some do not boil at all (sort of - usually enough heat will cause a chemical reaction and the result may have a boiling point). Can also refer to amino acids in biology. In agriculture, the soil and parts of the plant that are not usually used or sold. In math, the remainder in modular arithmetic.
This depends on the type of material. Uranium-238's half-life is 4,438,000,000 years. But the half-life of a material such as Radon-218 is only 35 ms. There is a great range of half-lives for a wide variety of isotopes, so it is impossible to generalize. If you're asking what a half-life is, it is the amount of time it takes for half of any quantity of a radioactive isotope to decay. So if you had a 10g pile of Uranium-238, after 4,438,000,000 years, only 5g of it would still be Uranium-238. The other half would've decayed.
The schoolboy left his bunk in his dormitory quietly before doing a bunk for the local town.---------------------------------------------------"Bunk" has several possible meanings. Here are some sample sentences using "bunk":Yes, I talked to her, and her version was total bunk.I prefer the top bunk.You can bunk with your brother.
he developed what we know today as calculus. he also "finished" many other theories that other "famus mathmations" before him left behind after they passed away.
It is the difference between sand running out of an hour glass and determining what time it is by how much sand is left. Radioactive decay happens at a steady rate. If you can determine how much of that radioactive isotope ought to have been in a sample at the start and you can measure how much is left, you can tell how much time has passed.
12.5%
If I take a radioactive sample of 400 moles of an unknown substance and let it decay to the point of three half-lives I would have 50 moles left of the sample. 1/2 of what is left will decay in the next half-life. At the end of that half-life I will have 25 moles left of the unknown substance or 4/25.
That would depend on the initial amount of the substance, as well as on its half-life.
Radioactive dating is carried out with substances which were formed at some unknown point in the past and contained a known proportion of a radioactive isotope of some element. Radioisotopes decay into other elements at a fixed and known rate. So, if you know how much of the radioactive isotope is still left in the sample, then you can work out how long it would have taken for the rest to have decayed into other elements. That gives the age of the sample.
12.5 g
Half-life is the length of time required for half the atoms in a radioactive sample to decay to some other type of atom. It is a logarithmic process, i.e. in one half-life, there is half the sample left, in two half-lives there is one quarter the sample left, in three half-lives there is one eight left, etc. The equation is... AT = A0 2 (-T/H) ... where A is activity, T is time, and H is half-life.
It disintegrates into its daughter nuclei that are much more stabler than the radioactive nuclei. If a sample of radioacictive material is left it will decay into another element over a period of time. Note that complete decay is not possible. A fraction of the original radioactive material will always remain in the sample.
After two minutes, half of the radioactive atoms will remain. After another two minutes, half of the remaining atoms will decay, leaving 1/4 of the original amount. Therefore, 1/4 of the radioactive atoms will be left after four minutes.
The half life is the time it takes for half the atoms in a given sample to decompose. Knowing this then after 27 days there is half the amount left. After 54 days then there is half that half left so that's a quarter.
It is the difference between sand running out of an hour glass and determining what time it is by how much sand is left. Radioactive decay happens at a steady rate. If you can determine how much of that radioactive isotope ought to have been in a sample at the start and you can measure how much is left, you can tell how much time has passed.
After 20 minutes, there have been 4 half-lives (20 min / 5 min per half-life). Each half-life reduces the sample by half, so the fraction of the sample left after 20 minutes is (1/2)^4, which is 1/16. Therefore, 1/16 of the original sample is left after 20 minutes.