The half-life of uranium-234 is approximately 25,000 years. How many undecayed nuclei remain after 100,000 years? Calculate the decay rate for uranium-234. If a sample contains 2.7 billion atoms of uranium-234 what is the rate of decay for that sample?

If a nucleus decays by β- decay to a daughter nucleus, which of the following statements about this decay are correct? (There may be more than one correct choice.) Explain why they are correct or incorrect.  A) The daughter nucleus has more protons than the original nucleus. B) The daughter nucleus has more neutrons than the original nucleus. C) The daughter nucleus has the same number of nucleons as the original nucleus. D) The daughter nucleus has fewer protons than the original nucleus. E) The daughter nucleus has fewer neutrons than the original nucleus.

10. The radioactive isotope (82Sr) has a half-life of 25.4 days. A sample containing this isotope has an initial activity at (t = 0) of 4.50 × 108 Bq. Calculate the number of nuclei that will decay in the time interval between t₁ = 80.0 hours. for ssi nuclei ssf624 50 ssfo 30.0 hours and t2 sf60 s 60 ssf6

A moon rock collected by a U.S. Apollo mission is estimated to be 3.90 billion years old by uranium/lead dating. Assuming that the rock did not contain any lead when it was formed, what is the current mass of 20°Pb in the rock, if it currently contains 1.340 g of 238 U? The half-life of 238U is 4.47 × 10° years. 206Pb mass: 1.1 Incorrect

The mass defect for potassium-40 is: -___x10-28kg. (Give your answer with 3 sig digs and do not include units) Use mass of proton = 1.007276 u mass of neutron = 1.008665 u actual mass = 39.9687 u

The radioactive isotope (Nb) has a half-life of 35 days. A sample containing this isotope has an initial activity at (t = 0) of 4.5e8 Bq. Calculate the number of nuclei that will decay in the time interval between t = 38.0 hours and t = 50.0 hours.

The number of radioactive nuclei present at the start of an experiment is 5.38 × 10¹5. The number present twenty days later is 5.02 × 10¹4. What is the half-life (in days) of the nuclei?

What is the mass of 25.0 mCi of technetium-99m (Tc99m)Tc99m , which has a half-life of 6.00 h?

The half-life of this nucleus is 1.0 seconds. For the following times fill in the rest of the chart and predict the number of parent nuclei left and the number of new daughter nuclei produced.     Time (seconds) Number of half-lives Parent Nuclei Daughter nuclei 0.0                 Start 100 0 1.0 1 50 50 2.0 2 25 75 3.0 3 12   4.0 4     5.0 5     6.0 6     7.0 7     8.0 8     9.0 9     10 10

Plutonium-239 (atomic number 94) is a by-product of nuclear power plants. It decays via alpha and gamma decay. The half-life for the decay is 24100 years. What is the decay constant for Pu-239 expressed in inverse years and inverse seconds? If the sample of Pu-is measured to have an activity of 150 decays per second today, how many years would it take for the sample to reduce to an activity of 5 decays per second? How many Pu-239 nuclei are in the sample measured today?