Chapter 39, Problem 30A

(a)

To determine

The ranking of the isotopes by the number of atomic number of the final product.

Explanation of Solution

Introduction:

The atomic number of the radioactive material decrease by two units due to ejection of the alpha particle and the atomic number of the radioactive material increases by one unit due to ejection of the beta particle.

The atomic number of Th-234 increases by one unit by beta decay. So, the atomic number of new atom becomes 91.

The atomic number of the U-238 decreases by two units by alpha decay. So, the atomic number of new atom becomes 90.

The atomic number of the Pa-234 Increases by one unit by beta decay. So, the atomic number of new atom becomes 92.

The atomic number of the U-234 decreases by two units by alpha decay. So, the atomic number of new atom becomes 90.

Conclusion:

Thus, the ranking of the isotopes by the number of atomic number of the final product is C, A, B = D.

(b)

To determine

The ranking of the isotopes by the number of atomic mass of the final product.

Explanation of Solution

Introduction:

The atomic mass of the radioactive material decrease by four units due to ejection of the alpha particle and the atomic mass of the radioactive material remains unaffected due to ejection of the beta particle.

The atomic mass of Th-234 remains unaffected by beta decay. The atomic mass of U-238 decreases by four units by alpha decay. So, the atomic mass of new atom becomes 234.

The atomic mass of Pa-234 remains unaffected by beta decay. The atomic mass of U-234 decreases by four units by alpha decay. So, the atomic mass of new atom becomes 230.

Conclusion:

Thus, the ranking of the isotopes by the number of atomic mass of the final product is B, A = C, D.