---
title: "An unstable parent nucleus with mass number \\(A = 232\\) and atomic number \\(Z = 90\\) undergoes the four-step decay chain listed below.  I. Alpha decay to form nucleus \\(\\text{Y}_1\\) II. Beta-minus (\\(\\beta^-\\)) decay of nucleus \\(\\text{Y}_1\\) to form nucleus \\(\\text{Y}_2\\) III. Beta-minus (\\(\\beta^-\\)) decay of nucleus \\(\\text{Y}_2\\) to form nucleus \\(\\text{Y}_3\\) IV. Alpha decay of nucleus \\(\\text{Y}_3\\) to form nucleus \\(\\text{Y}_4\\)  | Option | Atomic Number of \\(\\text{Y}_2\\) | Mass Number of \\(\\text{Y}_4\\) | Atomic Number of \\(\\text{Y}_4\\) | |—|—|—|—| | (A) | 87 | 224 | 88 | | (B) | 89 | 228 | 86 | | (C) | 89 | 224 | 88 | | (D) | 91 | 224 | 90 |  Which row in the table correctly identifies the atomic number of intermediate nucleus \\(\\text{Y}_2\\) and the mass number and atomic number of final nucleus \\(\\text{Y}_4\\)?"
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url: "https://nerd-notes.com/ubq/123517/"
date_modified: "2026-09-28T12:00:00+00:00"
---

# An unstable parent nucleus with mass number \(A = 232\) and atomic number \(Z = 90\) undergoes the four-step decay chain listed below.

I. Alpha decay to form nucleus \(\text{Y}_1\)
II. Beta-minus (\(\beta^-\)) decay of nucleus \(\text{Y}_1\) to form nucleus \(\text{Y}_2\)
III. Beta-minus (\(\beta^-\)) decay of nucleus \(\text{Y}_2\) to form nucleus \(\text{Y}_3\)
IV. Alpha decay of nucleus \(\text{Y}_3\) to form nucleus \(\text{Y}_4\)

| Option | Atomic Number of \(\text{Y}_2\) | Mass Number of \(\text{Y}_4\) | Atomic Number of \(\text{Y}_4\) |
|—|—|—|—|
| (A) | 87 | 224 | 88 |
| (B) | 89 | 228 | 86 |
| (C) | 89 | 224 | 88 |
| (D) | 91 | 224 | 90 |

Which row in the table correctly identifies the atomic number of intermediate nucleus \(\text{Y}_2\) and the mass number and atomic number of final nucleus \(\text{Y}_4\)?

An unstable parent nucleus with mass number \(A = 232\) and atomic number \(Z = 90\) undergoes the four-step decay chain listed below.

I. Alpha decay to form nucleus \(\text{Y}_1\)
II. Beta-minus (\(\beta^-\)) decay of nucleus \(\text{Y}_1\) to form nucleus \(\text{Y}_2\)
III. Beta-minus (\(\beta^-\)) decay of nucleus \(\text{Y}_2\) to form nucleus \(\text{Y}_3\)
IV. Alpha decay of nucleus \(\text{Y}_3\) to form nucleus \(\text{Y}_4\)

| Option | Atomic Number of \(\text{Y}_2\) | Mass Number of \(\text{Y}_4\) | Atomic Number of \(\text{Y}_4\) |
|---|---|---|---|
| (A) | 87 | 224 | 88 |
| (B) | 89 | 228 | 86 |
| (C) | 89 | 224 | 88 |
| (D) | 91 | 224 | 90 |

Which row in the table correctly identifies the atomic number of intermediate nucleus \(\text{Y}_2\) and the mass number and atomic number of final nucleus \(\text{Y}_4\)?

- **A.** Atomic number of \(\text{Y}_2\): 87 | Mass number of \(\text{Y}_4\): 224 | Atomic number of \(\text{Y}_4\): 88
- **B.** Atomic number of \(\text{Y}_2\): 89 | Mass number of \(\text{Y}_4\): 228 | Atomic number of \(\text{Y}_4\): 86
- **C.** Atomic number of \(\text{Y}_2\): 89 | Mass number of \(\text{Y}_4\): 224 | Atomic number of \(\text{Y}_4\): 88
- **D.** Atomic number of \(\text{Y}_2\): 91 | Mass number of \(\text{Y}_4\): 224 | Atomic number of \(\text{Y}_4\): 90

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123517/*