Question

Which of the following hydrogen like species will have same radius as that of a Bohr orbit of hydrogen atom?

• A. $n=2,{Li}^{2+}$
• B. $n=2,B{e}^{3+}$
• C. $n=2,H{e}^{+}$
• D. $n=3,L{i}^{2+}$

Answer 1

Answer: (B)

$n=2,B{e}^{3+}$

$r=\frac{n^2{r}_{l\left(H^{+}\right)}}{Z}$
$\because r=r\left(H^{+}\right)$ $.\cdot .n^2=Z.\cdot .n=2,Z=4$

So, $r_{2\left(B{e}^{+3}\right)}=r_{1\left(H^{+}\right)}$

Hence option B is correct.