Question

The mass number of an element in a radioactive series is 223. Then the radioactive series is ................

• A. 4n
• B. 4n+3
• C. 4n+2
• D. 4n+1

Answer 1

Answer: (B)

4n+3

$\begin{array}{cc}\text{mass number}=223& \\ \text{1)}4n+1=223& \\ n=\frac{222}{4}& \text{n}\notin \text{integer}\end{array}$

$\begin{array}{cc}2)4n+2& =223\\ n& =\frac{221}{4}\\ n& \notin \text{integer}\end{array}$

$\begin{array}{c}\text{3)}4n+3=223\\ n=55\\ n\in integen\\ \text{hence it is}4n+3\text{series}\\ \text{i.e. Option B is correct}\end{array}$