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Ch.20 - Nuclear Chemistry
Chapter 20, Problem 63

The radioisotope 226Ac can decay by any of three different nuclear processes: alpha emission, beta emission, or electron capture. (a) Write a balanced nuclear equation for the decay of 226Ac by each decay mode.

Verified step by step guidance
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Step 1: Identify the initial isotope and its atomic number. The isotope given is 226Ac, which has an atomic number of 89 (Actinium).
Step 2: Write the nuclear equation for alpha emission. In alpha decay, the nucleus emits an alpha particle, which is a helium nucleus (\( ^4_2He \)). This reduces the mass number by 4 and the atomic number by 2.
Step 3: Write the nuclear equation for beta emission. In beta decay, a neutron is converted into a proton, and a beta particle (\( ^0_{-1}e \)) is emitted. This increases the atomic number by 1 while the mass number remains unchanged.
Step 4: Write the nuclear equation for electron capture. In electron capture, an inner orbital electron is captured by the nucleus, which combines with a proton to form a neutron. This decreases the atomic number by 1 while the mass number remains unchanged.
Step 5: Balance each nuclear equation by ensuring that the sum of the mass numbers and the sum of the atomic numbers are equal on both sides of the equation.
Related Practice
Textbook Question
Radioactive decay exhibits a first-order rate law, rate = -∆N/∆t = kN, where N denotes the number of radio-active nuclei present at time t. The half-life of strontium-90, a dangerous nuclear fission product, is 29 years. (a) What fraction of the strontium-90 remains after three half-lives?
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Textbook Question
Potassium ion, K+, is present in most foods and is an essen-tial nutrient in the human body. Potassium-40, however, which has a natural abundance of 0.0117%, is radioactive with t1/2 = 1.25 x 10^9 years. What is the decay constant of 40K? How many 40K+ ions are present in 1.00 g of KCl? How many disintegration/s does 1.00 g of KCl undergo?
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Textbook Question
The electronic systems on the New Horizons spacecraft, which launched on January 19, 2006, and reached its closest approach to Pluto on July 14, 2015, were powered by elec-tricity generated by heat. The heat came from the radioac-tive decay of 238Pu in the 11 kg of 238PuO2 fuel onboard. The generator provided 240 W when the spacecraft was launched. If the power output is directly proportional to the amount of 238Pu in the generator, what was the power output when the spacecraft reached Pluto? The half-life of 238Pu is 87.7 y.
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Open Question
What is the 14C activity in decay events per minute of 1.0 g of a 3000-year-old wooden object? All living organisms contain an equilibrium concentration of radioactive 14C that gives rise to an average of 15.3 nuclear decay events per minute per gram of carbon. (14C, t1/2 = 5715 years)
Textbook Question
Uranium-238 has a half-life of 4.47 * 109 years and decays through a series of events to yield lead-206. Estimate the age of a rock that contains 105 mmol of 238U and 33 mmol of 206Pb. Assume all the 206Pb is from the decay of 238U.
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Textbook Question
The age of an igneous rock that has solidified from magma can be found by analyzing the amount of 40K and 40Ar. Potassium-40 emits a positron to produce argon-40 and the half-life of 40K is 1.25 * 109 years. What is the age of a rock whose 40Ar/40K ratio is 1.42?
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