if you started with 1000 grams of radium, how many grams would be left after 3 half lives?
954208
125\n\nie 1000/2 = 500 (1st half life)\n500/2 = 250 (2nd half life)\n250/2 = 125 (3rd half life)
678665
Which isotope?\n\nThorium-232 has a half-life of 14 billion (14x109) years, and decays by alpha emission, with accompanying gamma radiation. Thorium-232 is the top of a long decay series that contains key radionuclides such as radium-228, its direct decay product, and radon-220. \n\nTwo other isotopes of thorium, which can be significant in the environment, are thorium-230 and thorium-228. Both belong to other decay series. They also decay by alpha emission, with accompanying gamma radiation, and have half-lives of 75,400 years and 1.9 years, respectively
496225
1 mole = 6.022 * 10^23, so that's how many Rupees your are starting with.\n\nNow, to figure out how many seconds you live:\n\n60 seconds/min * 60 min/hour * 24 hour/day * 365.25 days/yr (factoring in leap years) * 90 yrs = 2840184000 = 2.84 * 10^9 seconds in your life\n\nThe portion depleted then would be:\n(2.84*10^9)/(6.022*10^23) = 4.71*10^(-15) = 0.00000000000000471\n\nSo the remaining quantity would be:\n1 - 0.00000000000000471 = 0.99999999999999529 \n\nConvert that to a percentage and you get 99.999999999999529%.\n\nSomebody double check my math there, please.
976396
1 G, I dont see how it can be zero otherwise it would float off!\n\nOK call me an idiot...I have just read the other answers lol
1007912
We did a similar lab in my math class. It will be about half whenever you flip 100 pennies, then half again, ect... This is roughly the same thing as the radioactive element ("half-life").\n\nNow, make sure you do the work so you will know the material, and explain the relationship in words your teacher would like to see.\n\nGood luck.
715558
OK, but you need to look up atomic weights or calculate molar mass.\n\n   Grams = Moles x molar mass  OR  moles x atomic mass\n\n    Moles = Grams/(molar mass) OR Grams/(atomic mass)
777912
Multiplu the time it takes to achieve half-life by the days required for a given amount of decay...\n\nSuch as 18.72 * .75\n\nI know you said not to give the answer, but you must understand that the question asks, how many days are required for 3/4 of the decay to decompose... \n\n The answer is by the days it takes for its half-life, multiplied by the desired ammount of decay.
249905
1 Dg equals to .1 grams.
940690
that would depend on the molarity of the substance. there could be any number of moles in that much solution.
915684
Very roughly:  by comparing the ratio between a radioisotope and its "daughter product", and with the knowledge of the radioisotope's half-life, calculate the amount of time needed for the observed ratio to develop.\n\nIn short, if there is a 50-50 split between the radioisotope and its daughter product, one half-life has passed.
168747
In radioactivity, it is the time taken for half of the nuclei in a given sample to decay (either by alpha or beta decay).  These vary form radioisotope to another.  For example Carbon-14 has a half life of 5700 years.  This means that if I have 1 gram of carbon-14, 5,700 years from now I will end up with 0.5grams (the rest would have become Nitrogen with beta decay).  If another 5,700 years pass I end up with 0.25g (!) and not 0g as common sense would indicate.  Each time a half life passes HALF the nuclei decay!In fact 'activity' decreases as time passes.\nAs said this time interval varies a lot.  The half life of Uranium-238 is 4,470,000,000 years, while that of thorium-230 is only 75,380 years.  Other half lives are quite short.  E.g. Iodine-131 has a half life of just 8 days and Sodium-24 has a half life of just 15 hours!
1026223
Because even though it is a radioactive element it's half-life will be over 1/2 million years making it a stable element.  It has what is termed in physics as an 'island of stability' which describes the possibility of elements which have stable 'magic numbers' of protons and neutrons.
212309
The half-lives will vary depending on the isotope.  Go to the library and look them up in "The Handbook of Chemistry and Physics" in the reference section.
132551
3 and a half grams.  An 8th of an ounce.
851600
Theoretically, it will just keep halving for all of time, but this is just statistics. When there's too few atoms of the radioactive element, for statistics to apply, the half-life is no longer valid.\nFor practical uses, it is assumed that the element is roughly gone after 10 half-lives, so after 10-12 hours the effect should be negligible
776529
The number of protons in the fission product must be 92-55 = 37.  The number of neutrons must be 1+235-143-3 = 90.  Look up in the periodic table to see what element 37 is. It is virtually certain that 90 neutrons are too many for stability, and the product will be a beta emitter.
238368
9000 grams. kilo=1000