Figure 42-20 shows part of the decay scheme of ^237 Np on a plot of mass number A versus proto

step 1 For this problem on the topic of nuclear physics, we are shown in the plot a part of the decay s

Figure 42-20 shows part of the decay scheme of ^237 Np on...

Figure 42-20 shows part of the decay scheme of ${ }^{237} \mathrm{~Np}$ on a plot of mass number $A$ versus proton number $Z$; five lines that represent either alpha decay or beta-minus decay connect dots that represent isotopes. What is the isotope at the end of the five decays (as marked with a question mark in Fig. $42-20$ ) ?

Key Concepts

Decay Chain

A decay chain is a sequential series of radioactive decays that leads from an unstable parent nucleus to a more stable daughter nucleus. In each step, the nucleus undergoes a specific type of decay—such as alpha or beta-minus decay—that alters its mass and/or proton numbers in predictable ways, mapping a trajectory across the nuclear chart.

Mass Number and Proton Number

The mass number (A) represents the total number of nucleons (protons and neutrons) in a nucleus, while the proton number (Z) indicates the number of protons, which determines the chemical identity of the element. In nuclear decay schemes, plotting A versus Z helps to visually track how various decay processes alter the nucleus over a chain of decays.

Alpha Decay

Alpha decay is a process by which an unstable nucleus emits an alpha particle, which is essentially a helium nucleus composed of 2 protons and 2 neutrons. This emission results in a decrease of the mass number by 4 and the atomic number by 2, transforming the original nucleus into a new element that is two places lower on the periodic table.

Beta-Minus Decay

Beta-minus decay is a type of radioactive decay in which a neutron inside the nucleus is converted into a proton, accompanied by the emission of an electron (beta particle) and an antineutrino. This conversion increases the atomic number by one while leaving the mass number unchanged, thereby moving the element one place to the right in the periodic table.

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