Indietro
Problema 19a
Predict the type of radioactive decay process for the following radionuclides: (a) 85B.
Problema 19b
Predict the type of radioactive decay process for the following radionuclides: (b) 6829Cu.
Problema 19c,d
Predict the type of radioactive decay process for the following radionuclides: (c) phosphorus-32. (d) chlorine-39.
Problema 20a
Each of the following nuclei undergoes either beta decay or positron emission. Predict the type of emission for each: (a) tritium, 31H.
Problema 20b
Each of the following nuclei undergoes either beta decay or positron emission. Predict the type of emission for each: b. 9938Sr
- One of the nuclides in each of the following pairs is radioactive. Predict which is radioactive and which is stable: (a) 39₁₉K and 40₁₉K. (b) ²⁰⁹Bi and ²⁰⁸Bi. (c) nickel-58 and nickel-65.
Problema 21
- One nuclide in each of these pairs is radioactive. Predict which is radioactive and which is stable: (a) 4020Ca and 4520Ca. Explain your choice in each case. (b) 12C and 14C. Explain your choice in each case. (c) lead-206 and thorium-230. Explain your choice in each case.
Problema 22
- Which of the following nuclides have magic numbers of both protons and neutrons: (a) helium-4, (b) oxygen-18, (c) calcium-40, (d) zinc-66, (e) lead-208?
Problema 23
Problema 24
Despite the similarities in the chemical reactivity of elements in the lanthanide series, their abundances in Earth's crust vary by two orders of magnitude. This graph shows the relative abundance as a function of atomic number. Which of the following statements best explains the sawtooth variation across the series? (a) The elements with an odd atomic number lie above the belt of stability. (b) The elements with an odd atomic number lie below the belt of stability. (c) The elements with an even atomic number have a magic number of protons. (d) Pairs of protons have a special stability.
- Which of the following statements best explains why alpha emission is relatively common, but proton emission is extremely rare? (a) Alpha particles are very stable because of magic numbers of protons and neutrons. (b) Alpha particles occur in the nucleus. (c) Alpha particles are the nuclei of an inert gas. (d) An alpha particle has a higher charge than a proton.
Problema 25
Problema 26
Which of the following nuclides would you expect to be radioactive: 5826Fe, 6027Co, 9241Nb, mercury-202, radium-226? Justify your choices.
- Which statement best explains why nuclear transmutations involving neutrons are generally easier to accomplish than those involving protons or alpha particles? (a) Neutrons are not a magic number particle. (b) Neutrons do not have an electrical charge. (c) Neutrons are smaller than protons or alpha particles. (d) Neutrons are attracted to the nucleus even at long distances, whereas protons and alpha particles are repelled.
Problema 27
- In 1930, the American physicist Ernest Lawrence designed the first cyclotron in Berkeley, California. In 1937, Lawrence bombarded a molybdenum target with deuterium ions, producing for the first time an element not found in nature. What was this element? Starting with molybdenum-96 as your reactant, write a nuclear equation to represent this process.
Problema 28
Problema 29b
Complete and balance the following nuclear equations by supplying the missing particle: (b) 21H + 32He → 42He + ?
Problema 29d
Complete and balance the following nuclear equations by supplying the missing particle: (d) 12253I → 12254Xe + ?
Problema 29e
Complete and balance the following nuclear equations by supplying the missing particle: (e) 5926Fe → 0-1e + ?
Problema 30a
Complete and balance the following nuclear equations by supplying the missing particle: (a) 147N + 42He¡? + 11H
Problema 30d
Complete and balance the following nuclear equations by supplying the missing particle: (d) 5826Fe + 2 10n¡6027Co + ?
Problema 30e
Complete and balance the following nuclear equations by supplying the missing particle: (e) 23592U + 10n¡13554Xe + 2 10n + ?
- Write balanced equations for (a) 238922U + 1n -> 224194Pu. (b) 147N + 1a -> 1p + 178O. (c) 5626Fe + 1a -> 1b + 6029Cu.
Problema 31
- Write balanced equations for each of the following nuclear reactions: (a) 23892U + 10n → g + 23992U. (b) 168O + 11p → a + 179N. (c) 188O + 10n → b- + 199F.
Problema 32
- It has been suggested that strontium-90 (generated by nuclear testing) deposited in the hot desert will undergo radioactive decay more rapidly because it will be exposed to much higher average temperatures. (a) Is this a reasonable suggestion? (Section 14.5) (b) Does the process of radioactive decay have an activation energy, like the Arrhenius behavior of many chemical reactions (Section 14.5)?
Problema 34
Problema 35
Some watch dials are coated with a phosphor, like ZnS, and a polymer in which some of the 1H atoms have been replaced by 3H atoms, tritium. The phosphor emits light when struck by the beta particle from the tritium decay, causing the dials to glow in the dark. The half-life of tritium is 12.3 yr. If the light given off is assumed to be directly proportional to the amount of tritium, by how much will a dial be dimmed in a watch that is 50 yr old?
Problema 36
It takes 4 h 39 min for a 2.00-mg sample of radium-230 to decay to 0.25 mg. What is the half-life of radium-230?
Problema 37
Cobalt-60 is a strong gamma emitter that has a half-life of 5.26 yr. The cobalt-60 in a radiotherapy unit must be replaced when its radioactivity falls to 75% of the original sample. If an original sample was purchased in June 2021, when will it be necessary to replace the cobalt-60?
- How much time is required for a 6.25-mg sample of 51Cr to decay to 0.75 mg if it has a half-life of 27.8 days?
Problema 38
- Radium-226, which undergoes alpha decay, has a half-life of 1600 yr. (a) How many alpha particles are emitted in 5.0 min by a 10.0-mg sample of 226Ra?
Problema 39
Problema 41
The cloth shroud from around a mummy is found to have a 14C activity of 9.7 disintegrations per minute per gram of carbon as compared with living organisms that undergo 16.3 disintegrations per minute per gram of carbon. From the half-life for 14C decay, 5730 yr, calculate the age of the shroud.
- A wooden artifact from a Chinese temple has a 14C activity of 38.0 counts per minute as compared with an activity of 58.2 counts per minute for a standard of zero age. From the half-life for 14C decay, 5715 years, determine the age of the artifact.
Problema 42
Problema 43
Potassium-40 decays to argon-40 with a half-life of 1.27 * 109 yr. What is the age of a rock in which the mass ratio of 40Ar to 40K is 4.2?