Chemistry · 2025
NEET 2025 · 4 May · Code 45 · Q50
Energy and radius of first Bohr orbit of He^+ and Li^2+ are [Given R_H =2.18 × 10^-18 J, a_0=52.9 pm ]
Energy and radius of first Bohr orbit of $\displaystyle \mathrm{He}^{+}$and $\displaystyle \mathrm{Li}^{2+}$ are
[Given $\displaystyle \mathrm{R}_{\mathrm{H}}=2.18 \times 10^{-18} \mathrm{~J}, \mathrm{a}_0=52.9 \mathrm{pm}$ ]
Official answer
From NTA’s final answer key for this paper.
(1)
$$\begin{aligned}
& \mathrm{E}_{\mathrm{n}}\left(\mathrm{Li}^{2+}\right)=-19.62 \times 10^{-18} \mathrm{~J} ; \\
& \mathrm{r}_{\mathrm{n}}\left(\mathrm{Li}^{2+}\right)=17.6 \mathrm{pm} \\
& \mathrm{E}_{\mathrm{n}}\left(\mathrm{He}^{+}\right)=-8.72 \times 10^{-18} \mathrm{~J} \\
& \mathrm{r}_{\mathrm{n}}\left(\mathrm{He}^{+}\right)=26.4 \mathrm{pm}
\end{aligned}
$$
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NEET (UG) 2025 Chemistry question, with the answer from NTA’s final answer key. Where our answers come from.