The half-life of a radioactive isotope is 6h. We start w/ 10g of the isotope after 1 day there will be?
610525
B\n\n1 day = 24 hours\n4 half life periods\n\n10\n5\n2.5\n1.25\n.625
281343
Isotopes: Protium, Deuterium, Tritium (naturally occurring)\nOther isotopes (synthesized):\n\n============================================================\nIsotopes\nMain Article: Isotopes of hydrogen \nHydrogen is the only element that has different names for its isotopes. (During the early study of radioactivity, various heavy radioactive isotopes were given names, but such names are no longer used, although one element, radon, has a name that originally applied to only one of its isotopes.) The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, although this is not officially sanctioned. (The symbol P is already in use for phosphorus and is not available for protium.)\n\n1H \nThe most common isotope of hydrogen, this stable isotope has a nucleus consisting of a single proton; hence the descriptive, although rarely used, name protium. The spin of a protium atom is 1/2+. [6]\n\n2H \nThe other stable isotope is deuterium, with an extra neutron in the nucleus. Deuterium comprises 0.0184%–0.0082% of all hydrogen (IUPAC); ratios of deuterium to protium are reported relative to the VSMOW standard reference water. The spin of a deuterium atom is 1+.\n\n3H \nThe third naturally occurring hydrogen isotope is the radioactive tritium. The tritium nucleus contains two neutrons in addition to the proton. It decays through beta decay and has a half-life of 12.32 years. Tritium occurs naturally due to cosmic rays interacting with atmospheric gases. Like ordinary hydrogen, tritium reacts with the oxygen in the atmosphere to form T2O. This radioactive "water" molecule constantly enters the Earth's seas and lakes in the form of slightly radioactive rain, but its half-life is short enough to prevent a buildup of hazardous radioactivity. The spin of a tritium atom is 1/2+.\n\n4H \nHydrogen-4 was synthesized by bombarding tritium with fast-moving deuterium nuclei. It decays through neutron emission and has a half-life of 9.93696x10-23 seconds. The spin of a hydrogen-4 atom is 2-.\n\n5H \nIn 2001 scientists detected hydrogen-5 by bombarding a hydrogen target with heavy ions. It decays through neutron emission and has a half-life of 8.01930x10-23 seconds.\n\n6H \nHydrogen-6 decays through triple neutron emission and has a half-life of 3.26500x10-22 seconds.\n\n7H \nIn 2003 hydrogen-7 was created (article) at the RIKEN laboratory in Japan by colliding a high-energy beam of helium-8 atoms with a cryogenic hydrogen target and detecting tritons—the nuclei of tritium atoms—and neutrons from the breakup of hydrogen-7, the same method used to produce and detect hydrogen-5.\n============================================================\n\nWater: H2O (one).
712861
1. a nuclear reaction\n2. helium\n3. 92U239\n4. cadmium\n5. plutonium\n6. involve changes in the nucleus\n7. americium and curium\n8. atomic weight\n9. energy\n10. nucleus\n11. moderator\n12. cadmium\n13. remains the same\n14. increases\n15. increases\n16. decreases\n17. remains the same\n18. decreases\n19. remains the same (if I'm not mistaken ... please check whether there is any beta particles released ... if there any, then the answer should be decreased)\n20. increases
223643
because not all of it has turned into lead yet. a half life extends forever. the part that has not decayed is still uranium.
324543
This is where convention comes in. hehe.\n\nYou see, today "time" is defined based on a reference. We define one second as exactly 9,192,631,770 oscillations or cycles of the cesium atom's resonant frequency, replacing the old second that was defined in terms of the Earth's motions.\n\nThe "uncertainity" is due to the fact that our one second here ( where its based on the measurement of this number of oscilations )  is NOT 100% the same as compared to our measurement of one second based on the previous way.\n\nWhat was the previous way? Well, it bascially defines one second the other way around. What i mean here is that in the old days time is defined relative to the motion of the earth around the sun. Ancients defined the total time taken for the earth to finish one complete revolution around the sun as one year. Then they agreed that one year is approximately made up of 365 days. Each day is then divided into 24 hours. 1 hour is then considered as having 60 minutes where 1 minute comprises as 60 seconds.\n\nOf course to achieve the definition of time as how we have it now did not just come overnight. It took some time... hehe. I did not attempt a chronological development of the idea but just intend to shed some light on the subject. You can find further information on the link below.
486649
The question is a little bit muddled, but I think I get the idea.\n\nThe atoms that are exposing the age of things are those atoms that are, or were, radioactive.  Any radioactive material decays.  It also decays at predictable, measurable rates that are distinctive to the element.  So you can date things that have radioactive elements (which most things do in some trace amount) or their decay elements within, based on how decayed they are.\n\nUranium-238 ultimately decays into lead.  You can date how long something containing uranium-238 has been in existence based on the ratio of Ur-238 to Pb.\n\nThis process operates at the same rate no matter what the temperature is.
844938
The predicted figure is accurate but its accuracy depends on the size of the sample.The half life of an atomic species is an average figure based on a reasonably sized sample with a huge number of atoms. It's based upon the probability that any given atom will decay at a given time. For instance scientists can predict that a coin has a 50/50 chance of landing heads or tails when flipped. This means that if you flipped the coin 1000 times you could be reasonably certain that you would get close to 500 tails and 500 heads. This doesn't mean that if you flipped it four times you would get 2 heads and 2 tails each time. It's the same with the rate of decay. The decay occurs randomly in that scientists cannot predict when any given atom will decay anymore than you can predict exactly which flips will result in heads or tails. But the more atoms a sample has the more accurate the predicted rate of decay (half life).
951626
It is very simple.  This method will help you when the fraction is not a nice one like 1/16.\n\n\nAt time zero you have, let's say N0 = 1600 atoms of protactinium-234.  After 26.76 hours, 1/16 remain:\n\nNt = 1600 / 16 = 100.\n\nNow in radioactive decay:\n\nNt = N0 * exp (-Lamda * t).\n\nYou have t, Nt, N0.  Calculate lambda\n\n100 = 1600 exp (-Lambda * 26.76)\n0.0625 = exp (-Lambda * 26.76)\nTaking Ln on both sides\nLn 0.0625 = - Lambda * 26.76\nLambda = - (Ln 0.0625) / 26.76 = 0.10361 h^(-1)\n\nHalf life = (Ln 2) / Lambda = 6.69 hours
860007
5 Half-Lives.\n\nAfter 1: 200ng\nAfter 2: 100ng\nAfter 3: 50ng\nAfter 4: 25ng\nAfter 5: 12.5ng
882008
it's mass time the speed of light squared.  It's really not that much from one atom.  I posted the answer a few months ago, did you check to see if this was already asked?\n\n\nwe see that for heavy nuclides (mass about 240u), the mean biding energy per nucleon is about 7.6MeV. For middle-mass nuclides (mass about 120), it is about 8.5 MeV. This difference in total binding energy between a single large nucleus and two fragments (assumed to be equal) into which it may be split is then close to 200MeV. This is a relatively large amount of released energy per fission event. When a chain reaction occurs, many atoms and nuclei are involved so lots of energy is released.\nhttp://www.world-mysteries.com/sci_9.htm
414512
As soon as a living organism dies, it stops taking in new carbon. The ratio of carbon-12 to carbon-14 at the moment of death is the same as every other living thing, but the carbon-14 decays and is not replaced. The carbon-14 decays with its half-life of 5,700 years, while the amount of carbon-12 remains constant in the sample. By looking at the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing fairly precisely. \nA formula to calculate how old a sample is by carbon-14 dating is: \n\n\nt = [ ln (Nf/No) / (-0.693) ] x t1/2 \nwhere ln is the natural logarithm, Nf/No is the percent of carbon-14 in the sample compared to the amount in living tissue, and t1/2 is the half-life of carbon-14 (5,700 years). \n\nSo, if you had a fossil that had 10 percent carbon-14 compared to a living sample, then that fossil would be: \n\n\nt = [ ln (0.10) / (-0.693) ] x 5,700 years \nt = [ (-2.303) / (-0.693) ] x 5,700 years \n\nt = [ 3.323 ] x 5,700 years \n\nt = 18,940 years old \n\nBecause the half-life of carbon-14 is 5,700 years, it is only reliable for dating objects up to about 60,000 years old. However, the principle of carbon-14 dating applies to other isotopes as well. Potassium-40 is another radioactive element naturally found in your body and has a half-life of 1.3 billion years. Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).
636669
suppose u have 100gm of a radioactive material with half life as 5 yrs. after 5 yrs the amount will be 50gms as half of it has decayed in 5 yrs.In next 5 yrs it will reduce to 25 gms and so on . As the radioactive material decays to half of its initial amount so it is called half life of that material.
419931
Rather than radioactive element, let's call it a radioactive isotope.  Why?  Because a radioactive element can decay and still be the same element but have fewer neutrons.  As other posters sort of explained, if an isotope is radioactive then half of it should become something else in the specific half life time.  It could still be the same element, or it might be a lighter element.  Read the link about carbon dating and you might understand how this is useful.
1186362
False. Scientists realize that radioactive decay happens at a steady rate which can be measured by radio-carbon dating. Through countless tests over many years, the consistent measurements so far have indicated that the Earth is about 4 billion years old.
562664
Nuclear waste or any radiological material deteriorates in its radioactive properties at a set rate determined by spin of rates of the neutrons that orbit the nucelus of the specific molecule in question. This rate is know as a half life or the time it takes for half the neutrons to spin off. This can only be accelarated by forecfully adding electrons to the molecules of the material, which is another radiological procedure that requires large amounts of electricity.  A very expensive process.  Chemicals have virtualy no effect toward accelarating half rates.
541650
Very good question.  I went searching and came up with this:\n\nBTW, the person that answered 687 is correct for EARTH days, not MARS days.  It appears to be closer to 668.6 Martian days.
973296
hi Fellow Genius !,\ngood question.\n\nYES. Protons do decay. they have an average lifetime of about 10 to the power 32 years. Now, since this is an average, it should be possible to monitor a large enough collection of protons, and observe a few decays in the space of an year or so. Such experiments, involving 100s of tons of H2O or some other material, are underway in many parts of the world [eg.: a cave 600m below Lake Erie, Ohio]. However, none of them have yet [so far as I know] found any convincing evidence for the "predicted" decays of protons. [will answer part 2&3 of ur Q seperately] contact me at email address: fizamaker@hotmail.com or IM with me on Y!Messenger [ I am usually online from 9 pm to 5 am India time all night ]. my ID there is :  fizanaqsh . Add my ID to ur contacts so we can talk back and forth on physics and metaphysical questions bothering u and/ or me !  I have a Skype ID also and its : homeworknetguru.\ndo take the trouble of replying if my answer satisfies ur curiosity or not. i am v. much interested in these questions. look out for my answer 2 the third part of ur question re the "arrow of time"