Assuming the validity of Bohr's atomic model for hydrogen like ions the radius of $\mathrm{Li}^{++}$ion in…

Assuming the validity of Bohr's atomic model for hydrogen like ions the radius of $\mathrm{Li}^{++}$ion in its ground state is given by $\frac{1}{X} a_0$, where $X=$ _______. (Where $\mathrm{a}_0$ is the first Bohr's radius.)
  1. 2
  2. 1
  3. 3
  4. 9

Solution

$\mathrm{r}=\mathrm{r}_0 \frac{\mathrm{n}^2}{\mathrm{z}} \& \mathrm{z}=3$ for $\mathrm{Li}^{+2}$ and $\mathrm{n}=1$
$\therefore \mathrm{r}=\mathrm{r}_0 \frac{1^2}{3}=\frac{\mathrm{r}_0}{3} \quad \therefore \mathrm{x}=3$

Asked in: JEE Main 2025 (02 Apr Shift 2)

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