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What percentage of original radioactive atoms are left after 5 half lives?
Wiki User
∙ 11y ago
if you have 100g of a radioactive material with a half life of 5.0 years then, 5.0 years after the material was created there will be 50g of radioactive material left, another 5 years and it will be 25g, then another 5 years 12.5 radioactive material will be left, another 5 years, 6.25g, then 3.125g will be left after another 5 years, that is 25 years so what percent of 100 is 3.125? your answer is 3.125% of the material will be left
Wiki User
∙ 14y ago
Wiki User
∙ 11y agoIf at first there is 100 atoms
after 1 half lives there is 100/2=50 atoms
after 2 half lives there is 50/2=25 atoms
after 3 half lives there is 25/2=12.5 atoms
after 4 half lives there is 12.5/2=6.25 atoms
after 5 half lives there is 6.25/2=3.125 atoms
So there is 3.125% after 5 half lives.
left atoms after n half lives = original atoms/2^n
Better Answer: if we are talking about only 100 atoms and not in terms of percentage of a huge number of atoms:
Between 0 to 100 radioactive atoms will remain as the half life is only a statistical indication of the time taken for half of the number of atoms to decay.
So in reality, whether an atom will decay or not will depend essentially on chance rather than on something that is absolute.
When the number of atoms is huge i.e. in the billions or trillions, the reality will be more in line with the probability calculation.
However, when the number of atoms is as small as 100, the use of the probability calculation is not valid.
Wiki User
∙ 14y agoIf a riodisotope has decayed to 0.25 of its original amount, then 2 half-lifes has elspased.
AT = A0 2(-T/H)
0.25 = (1) 2(-T(1))
log2(0.25) = -T
T = 2
Wiki User
∙ 12y ago18 years.
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What percentage of a radioactive element will remain after seven half lives?
1/27 = 1/128 = 0.78125%
What does half-life of a radioactive sample mean?
A radioactive sample is constantly decaying. In the period of one half-life, 50% of the radioactive atoms are expected to decay to their stable fragments. After two half-lives, 75% of the radioactive atoms have decayed, and 25% of the original quantity remain.
What percentage of a radioactive species would be found as daughter material after seven half lives?
The equation for half-life is AT = A0 2 (-T / H) where A0 is the starting activity, AT is the activity at some time T, and H is half-life in units of T. As a result, seven half-lives would be 2(-7) or 0.0078125 of the original activity.
After three half lives have passed how much of the original radioactive material will remaim?
1/8th gram will be left. That's your answer.
How many years will it take for one half of the original amount of material to decay?
If you are referring to a radioactive material, that will depend on the material. Different things have very different half-lives.
What percentage of a radioactive sample remains after 5 half-lives?
3.1 %
What is the percentage of radioactive nuclei left after 3 half-lives have passed?
12.5%
How do radioisotopes of an element differ feom other isotopes?
Radioisotopes are "radioactive isotopes"; they are not stable. Radioactive atoms will decay, or break apart into other atoms, by emitting an electron, or a neutron or a positron or an alpha particle (2 protons and two neutrons). The rate at which this happens is measured by the "half-life"; after one half-life, half of the atoms will have decayed. After another half-life, half of the remaining atoms will have decayed. Atoms with short half-lives are highly radioactive, and can be fairly dangerous. Atoms with long half-lives are only slightly radioactive, and aren't all that dangerous.
What is the percentage of radioactive nuclei left after 3 half lives have passed?
12.5%
Which statement is true about half-lives a Different atoms of the same element have different half-lives. b Each radioactive isotope has its own half-life. c All radioactive nuclides of an element?
The correct answer is: Half-lives are not affected by temperature.
What percentage of a radioactive element will remain after seven half lives?
1/27 = 1/128 = 0.78125%
After three half-lives what fraction of a radioactive sample remains?
1/8 of the original amount remains.
How many half-lives have passed for 50 percent of the original radioactive material?
One half-life.
What fraction of a radioactive nuclei remain after p half lives?
The remainder is 2-p or 0.5p of the original amount.
Why is radioactive waste considered safe after 10 half lives?
I would consider it safe after 5 half-lives. by 5 it has decayed to 3% of original level, by 10 it has decayed to 0.1% of original level.
After 6 half-lives What percentage of a radioactive sample remain?
After 6 half lives, the remaining will be (1/2)6 i.e 1/64 th of the initial amount. Hence by percentage it would be 1.5625 %
What is the problem with disposing of radioactive wastes is that they have a long what?
Radioactive substances have half-lives. This is because the isotope constantly is changing from the radioactive isotope to a daughter element. For example, eventually, when uranium's radioactivity is gone, it becomes lead. After one half life of a radioactive substance, only 50% of that substance is still radioactive. Therefore, after one half-life, a piece of uranium is 50% lead and therefore %50 less radioactive. After another half-life, it has 25% of the original radioactivity, and 75% of the original uranium has become lead. This is the problem with radioactive wastes. It takes many years just for one half lives for some substances, such as uranium. Because radioactivity is harmful, those substances have to be stored until they are no longer radioactive. So, in short, the problem with disposing of radioactive wastes is that they have long half-lives. (although this is not true with ALL substances because some have short half-lives, but, in general, radioactive substances have long half-lives.
