Question

An element X decays first by positron emission and then two ?-particles are emitted in successive radioactive decay. If the product nucleus has mass number 227 and atomic number 89, the mass number and atomic number of element X are

• A. (273, 93)
• B. (235, 94)
• C. (238, 93)
• D. (237, 92)

Answer 1

Answer: (B)

(235, 94)

Answer 2

Let A and Z be mass number and atomic number of element X. ${^{A}_{Z}X ->[\beta^{+}]}$ ${^{A}_{Z-1}Y ->[2\alpha] ^{A-8}_{Z-5}Y'}$ Since the product nucleus has mass number $227$ and atomic number $89$. $\therefore\quad A - 8 = 227$ or $A = 235$ and $Z - 5 = 89$ or $Z = 94$