Physics · Composition and size of nucleus, atomic masses, mass-energy relation, mass defect

A radioactive nucleus undergoes a series of decays according to the scheme If th

A radioactive nucleus undergoes a series of decays according to the scheme \( \boldsymbol{A} \stackrel{\boldsymbol{\alpha}}{\longrightarrow} \boldsymbol{A}_{1} \stackrel{\boldsymbol{\beta}}{\longrightarrow} \boldsymbol{A}_{2} \stackrel{\boldsymbol{\alpha}}{\longrightarrow} \boldsymbol{A}_{3} \stackrel{\gamma}{\longrightarrow} \boldsymbol{A}_{4} \) If the mass number and atomic number of \( A \) are 180 and \( 72, \) respectively, then what are these number for \( \boldsymbol{A}_{4} \) ?

  • A. 172 and 69
  • B. 174 and 70
  • C. 176 and 69
  • D. 176 and 70

Step-by-step solution

Start with A (Z=72, A=180). After α decay: Z decreases by 2, A decreases by 4 → A1 (Z=70, A=176). After β decay: Z increases by 1, A unchanged → A2 (Z=71, A=176). After α decay: Z decreases by 2, A decreases by 4 → A3 (Z=69, A=172). γ decay does not change Z or A, so A4 has Z=69, A=172.
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