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Chapter 16: Problem 61

What happens to an atom's atomic number and mass number when it undergoes alpha emission?

Short Answer

Expert verified
When an atom undergoes alpha emission, its atomic number decreases by 2 (\(Z - 2\)) and its mass number decreases by 4 (\(A - 4\)).

Step by step solution

01

Introduction to Alpha Emission

Alpha emission is a type of radioactive decay in which an unstable atomic nucleus loses two protons and two neutrons in the form of an alpha particle. The alpha particle is essentially a helium-4 nucleus, which consists of 2 protons and 2 neutrons.
02

Impact of Alpha Emission on Atomic Number

The atomic number (Z) of an element is the number of protons in its nucleus. Since an alpha particle contains 2 protons, when an atom undergoes alpha emission, it loses 2 protons in the process. Thus, the atomic number of the resulting atom decreases by 2. In other words, if the original atomic number was \(Z\), the atomic number of the new atom after alpha emission will be \(Z - 2\).
03

Impact of Alpha Emission on Mass Number

The mass number (A) of an atom is the total number of protons and neutrons in its nucleus. An alpha particle contains a total of 4 nucleons (2 protons and 2 neutrons). Therefore, when an atom undergoes alpha emission and releases an alpha particle, it loses a total of 4 nucleons. Consequently, the mass number of the resulting atom decreases by 4. If the original mass number was \(A\), the mass number of the new atom after alpha emission will be \(A - 4\). In summary, when an atom undergoes alpha emission, its atomic number decreases by 2 and its mass number decreases by 4.

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Most popular questions from this chapter

Pockets of trapped helium gas are found near some deposits of radioactive ores. How can you explain this?

Consider the radioactive decay of radium to radon: \({ }_{88}^{226} \mathrm{Ra} \rightarrow{ }_{86}^{222} \mathrm{Rn}+?\) (a) Write the complete equation. (b) What type of decay is this? (c) Explain why radium-226 is likely to undergo the type of decay you named in part (b). (d) How much energy is released, in kilojoules, when 1 mole of \({ }^{226}\) Ra decays? [Molar masses: \({ }_{88}^{226} \mathrm{Ra}, 226.0254 \mathrm{~g} / \mathrm{mol} ;{ }_{86}^{222} \mathrm{Rn}, 222.0175 \mathrm{~g} / \mathrm{mol}\) \(\left.{ }_{2}^{4} \mathrm{He}, 4.0026036 \mathrm{~g} / \mathrm{mol}\right]\) (e) How much energy is released, in kilojoules, when \(1 \mathrm{~g}\) of \({ }_{88}^{226}\) Ra decays?

The isotopes \({ }^{17} \mathrm{~F}^{20} \mathrm{~F}\), and \({ }^{21} \mathrm{~F}\) are all radioactive, decaying either by beta emission or by positron emission. Name the decay process for each isotope.

The tungsten isotope \({ }_{74}^{162} \mathrm{~W}\) is radioactive and decays by converting a proton to a neutron. (a) Where is this atom likely to lie in the band of stability? (b) Write two nuclear reactions that describe this decay process. (c) Which type of decay is represented by each reaction you wrote in part (b)?

The thorium isotope \({ }_{90}^{232}\) Th is radioactive and decays by ejecting two protons and two neutrons from its nucleus. (a) Where is this atom likely to lie in the band of stability? (b) Write a nuclear reaction for this decay process. (c) Which type of decay is this?
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