NEET UG 2010 — Chemistry Inorganic Chemistry

2010mcqmedium

Which one of the following species does not exist under normal conditions ?

Official previous-year question

Held on 30 Apr 2010 · Verified 9 Jul 2026.

Options

A
$\mathrm{Be}_2^{+}$
B
$\mathrm{Be}_2$
C
$\mathrm{B}_2$
D
$\mathrm{Li}_2$

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Solution

Key Idea Molecules with zero bond order, do not exist. (a) $\mathrm{Be}_2^{+}(4+4-1=7)=$ $\begin{aligned} & \sigma 1 \mathrm{~s}^2, \sigma 1 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^1 \\ & \mathrm{BO}=\frac{4-3}{2}=0.5 \end{aligned}$ (b) $\mathrm{Be}_2(4+4=8)=\sigma 1 \mathrm{~s}^2, \sigma 1 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^2$ $\mathrm{BO}=\frac{4-4}{2}=0$ (c) $\mathrm{B}_2(5+5=10)$ $\begin{gathered} =\sigma 1 \mathrm{~s}^2, \sigma 1 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^2, \pi 2 p_{\mathrm{x}}^1 \approx \pi 2 \mathrm{p}_{\mathrm{y}}^1 \\ \mathrm{BO}=\frac{6-4}{2}=1 \end{gathered}$ (d) $\begin{aligned} & \operatorname{Li}_2(3+3=6) \\ & =\sigma 1 \mathrm{~s}^2, \sigma 1 \mathrm{~s}^2, \sigma 2 \mathrm{~s}^2 \\ & =\frac{4-2}{2}=1 \end{aligned}$ $\mathrm{BO}=\frac{4-2}{2}=1$ Thus, $\mathrm{Be}_2$ does not exist under normal conditions.

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NEET UG 2010 — Chemistry Inorganic Chemistry

2010mcqmedium

Which one of the following species does not exist under normal conditions ?

Official previous-year question

Held on 30 Apr 2010 · Verified 9 Jul 2026.

Options

A
$\mathrm{Be}_2^{+}$
B
$\mathrm{Be}_2$
C
$\mathrm{B}_2$
D
$\mathrm{Li}_2$

Did you get this right?

Solution

Your note

NEET UG Inorganic Chemistry in other years

Keep practicing Inorganic Chemistry

Work through every NEET UG Inorganic Chemistry PYQ, year by year.

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NEET UG 2010 — Chemistry Inorganic Chemistry

Options

Did you get this right?

Solution

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NEET UG Inorganic Chemistry in other years

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NEET UG 2010 — Chemistry Inorganic Chemistry

Options

Did you get this right?

Solution

Your note

NEET UG Inorganic Chemistry in other years

More NEET UG Inorganic Chemistry questions

Other Chemistry topics for NEET UG

Physical Chemistry

Organic Chemistry

Keep practicing Inorganic Chemistry