Question

The three isotopes of ${}_{86}\text{Rn}$ formed as an intermediate during decay of ${}^{232}\text{Th}{,}^{238}\text{U}$ and ${}^{235}\text{U}$ series does not contain the isotope :

• A. thoron, ${}_{86}^{220}\text{Rn}$ in thorium series
• B. radon, ${}_{86}^{222}\text{Rn}$ in uranium series
• C. actinon, ${}_{86}^{219}\text{Rn}$ in actinium series
• D. actinon, ${}_{86}^{220}\text{Rn}$ in actinium series

Answer 1

Answer: (D)

actinon, ${}_{86}^{220}\text{Rn}$ in actinium series

Actinium series: $4n+3$
Np series: $4n+1$
Radium series: $4n+2$
Thorium series: $4n$
$\frac{Massno.ofRn}{4}=55$, thus, it cannot be in actinium series (4n + 3).