jee main chemistry important questions | Chemical Bonding And Molecular Structure

Q 1 :
Number of molecules/species from the following having one unpaired electron is __________.

$O_{2}, O_{2}^{- 1}, NO, {CN}^{- 1}, O_{2}^{2 -}$ [2024]

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Molecules	Number of electrons	Electronic configuration	Number of unpaired electrons
$O_{2}$	16	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{1} = π^{} 2 p_{y}^{1}$	2
$O_{2}^{-}$	17	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{2} = π^{} 2 p_{y}^{1}$	1
$NO$	15	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{1} = π^{} 2 p_{y}^{0}$	1
${CN}^{-}$	14	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < σ 2 p_{z}^{2}$	0
$O_{2}^{2 -}$	18	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{2} = π^{} 2 p_{y}^{2}$	0

Q 2 :
Number of molecules having bond order 2 from the following molecule is _________ .

$C_{2}, O_{2}, B e_{2}, L i_{2}, N e_{2}, N_{2}, H e_{2}$ [2024]

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Molecule	Electronic configuration	Bond order $= \frac{1}{2} [N_{b} - N_{a}]$
$C_{2}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2}$	$\frac{1}{2} [8 - 4] = 2$
$O_{2}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{1} = π^{} 2 p_{y}^{1}$	$\frac{1}{2} [10 - 6] = 2$
${Be}_{2}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2}$	$\frac{1}{2} [4 - 4] = 0$
${Li}_{2}$	$σ 1 s^{2} < σ^{*} 1 s^{2} < σ 2 s^{2}$	$\frac{1}{2} [4 - 2] = 1$
${Ne}_{2}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{2} = π^{} 2 p_{y}^{2} < σ^{*} 2 p_{z}^{2}$	$\frac{1}{2} [10 - 10] = 0$
$N_{2}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < σ 2 p_{z}^{2}$	$\frac{1}{2} [10 - 4] = 3$
${He}_{2}$	$σ 1 s^{2} < σ^{*} 1 s^{2}$	$\frac{1}{2} [2 - 2] = 0$

Q 3 :
The total number of species from the following in which one unpaired electron is present, in ____________ .

$N_{2}, O_{2}, C_{2}^{-}, O_{2}^{-}, O_{2}^{2 -}, H_{2}^{+}, {CN}^{-}, {He}_{2}^{+}$ [2024]

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Molecule	Electronic configuration	Number of unpaired electrons
$N_{2}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < σ 2 p_{z}^{2}$	0
$O_{2}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{1} = π^{} 2 p_{y}^{1}$	2
$C_{2}^{-}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < σ 2 p_{z}^{1}$	1
$O_{2}^{-}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{2} = π^{} 2 p_{y}^{1}$	1
$O_{2}^{2 -}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{2} = π^{} 2 p_{y}^{2}$	0
$H_{2}^{+}$	$σ 1 s^{1}$	1
${CN}^{-}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < σ 2 p_{z}^{2}$	0
${He}_{2}^{+}$	$σ 1 s^{2} < σ^{*} 1 s^{1}$	1

Q 4 :
Total number of electrons present in $(π^{*})$ molecular orbitals of $O_{2}, O_{2}^{+}$ and $O_{2}^{-}$ is _________ . [2024]

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Molecule	Electronic configuration	*Electrons present in $π^{}$**
$O_{2}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{1} = π^{} 2 p_{y}^{1}$	2
$O_{2}^{+}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{1} = π^{} 2 p_{y}^{0}$	1
$O_{2}^{-}$	$σ 1 s^{2} < σ^{} 1 s^{2} < σ 2 s^{2} < σ^{} 2 s^{2} < σ 2 p_{z}^{2} < π 2 p_{x}^{2} = π 2 p_{y}^{2} < π^{} 2 p_{x}^{2} = π^{} 2 p_{y}^{1}$	3

Sum = 2 + 1 + 3 = 6

Q 5 :
When $ψ_{A}$ and $ψ_{B}$ are the wave function of atomic orbitals, then $σ^{*}$ is represented by: [2024]

$ψ_{A} - 2 ψ_{B}$
$ψ_{A} + ψ_{B}$
$ψ_{A} + 2 ψ_{B}$
$ψ_{A} - ψ_{B}$

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Constructive overlap of wavefunctions $(ψ_{A} + ψ_{B})$ give bonding molecular orbital ( $σ$ or $π$ ) and destructive overlap of wavefunctions $(ψ_{A} - ψ_{B})$ give antibonding molecular orbitals ( $σ^{*}$ or $π^{*}$ ). Axial overlap of orbitals give $σ$ (or $σ^{*}$ ) bond and lateral overlap of orbitals give $π$ (or $π^{*}$ ) bond.

Q 6 :
Which of the following linear combination of atomic orbitals will lead to formation of molecular orbitals in homonuclear diatomic molecules [internuclear axis in z-direction]?

(A)   $2 p_{z}$ and $2 p_{x}$

(B)   $2 s$ and $2 p_{x}$

(C)   $3 d_{x y}$ and $3 d_{x^{2} - y^{2}}$

(D)   $2 s$ and $2 p_{z}$

(E)   $2 p_{z}$ and $3 d_{x^{2} - y^{2}}$

Choose the correct answer from the options given below:   [2025]

(A) and (B) only
(E) only
(D) only
(C) and (D) only

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Q 7 :
Which of the following molecules(s) show/s paramagnetic behavior? [2025]

(A)   $O_{2}$
(B)   $N_{2}$
(C)   $F_{2}$
(D)   $S_{2}$
(E)   ${Cl}_{2}$

Choose the correct answer from the options given below:

B only
A and C only
A and E only
A and D only

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Molecule	Electronic Configuration	Number of Unpaired Electrons	Magnetic Nature
$O_{2}$	$σ 1 s^{2}, σ^{} 1 s^{2}, σ 2 s^{2}, σ^{} 2 s^{2}, σ 2 p_{z}^{2}, π 2 p_{x}^{2}, π 2 p_{y}^{2}, π^{} 2 p_{x}^{1}, π^{} 2 p_{y}^{1}$	2	Paramagnetic
$N_{2}$	$σ 1 s^{2}, σ^{} 1 s^{2}, σ 2 s^{2}, σ^{} 2 s^{2}, π 2 p_{x}^{2}, π 2 p_{y}^{2}, σ 2 p_{z}^{2}$	0	Diamagnetic
$F_{2}$	$σ 1 s^{2}, σ^{} 1 s^{2}, σ 2 s^{2}, σ^{} 2 s^{2}, σ 2 p_{z}^{2}, π 2 p_{x}^{2}, π 2 p_{y}^{2}, π^{} 2 p_{x}^{2}, π^{} 2 p_{y}^{2}$	0	Diamagnetic
$S_{2}$	$KK, LL, σ 3 s^{2}, σ^{} 3 s^{2}, σ 3 p_{z}^{2}, π 3 p_{x}^{2}, π 3 p_{y}^{2}, π^{} 3 p_{x}^{1}, π^{*} 3 p_{y}^{1}$	2	Paramagnetic
${Cl}_{2}$	$KK, LL, σ 3 s^{2}, σ^{} 3 s^{2}, σ 3 p_{z}^{2}, π 3 p_{x}^{2}, π 3 p_{y}^{2}, π^{} 3 p_{x}^{2}, π^{*} 3 p_{y}^{2}$	0	Diamagnetic

Topic Question Set

Q 1 :
Number of molecules/species from the following having one unpaired electron is __________.

$O_{2}, O_{2}^{- 1}, NO, {CN}^{- 1}, O_{2}^{2 -}$ [2024]

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Q 2 :
Number of molecules having bond order 2 from the following molecule is _________ .

$C_{2}, O_{2}, B e_{2}, L i_{2}, N e_{2}, N_{2}, H e_{2}$ [2024]

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Q 3 :
The total number of species from the following in which one unpaired electron is present, in ____________ .

$N_{2}, O_{2}, C_{2}^{-}, O_{2}^{-}, O_{2}^{2 -}, H_{2}^{+}, {CN}^{-}, {He}_{2}^{+}$ [2024]

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Q 4 :
Total number of electrons present in $(π^{*})$ molecular orbitals of $O_{2}, O_{2}^{+}$ and $O_{2}^{-}$ is _________ . [2024]

0%

Q 5 :
When $ψ_{A}$ and $ψ_{B}$ are the wave function of atomic orbitals, then $σ^{*}$ is represented by: [2024]

Q 7 :
Which of the following molecules(s) show/s paramagnetic behavior? [2025]

(A)   $O_{2}$
(B)   $N_{2}$
(C)   $F_{2}$
(D)   $S_{2}$
(E)   ${Cl}_{2}$

Choose the correct answer from the options given below:

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Topic Question Set

Q 1 : Number of molecules/species from the following having one unpaired electron is __________. O2,O2-1,NO,CN-1,O22- [2024]

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Q 2 : Number of molecules having bond order 2 from the following molecule is _________ . C2,O2,Be2,Li2,Ne2,N2,He2 [2024]

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Q 3 : The total number of species from the following in which one unpaired electron is present, in ____________ . N2,O2,C2-,O2-,O22-,H2+,CN-,He2+ [2024]

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Q 4 : Total number of electrons present in (π*) molecular orbitals of O2,O2+ and O2- is _________ . [2024]

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Q 5 : When ψA and ψB are the wave function of atomic orbitals, then σ* is represented by: [2024]

Q 7 : Which of the following molecules(s) show/s paramagnetic behavior? [2025] (A) O2 (B) N2 (C) F2 (D) S2 (E) Cl2 Choose the correct answer from the options given below:

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Q 1 :
Number of molecules/species from the following having one unpaired electron is __________.

$O_{2}, O_{2}^{- 1}, NO, {CN}^{- 1}, O_{2}^{2 -}$ [2024]

Q 2 :
Number of molecules having bond order 2 from the following molecule is _________ .

$C_{2}, O_{2}, B e_{2}, L i_{2}, N e_{2}, N_{2}, H e_{2}$ [2024]

Q 3 :
The total number of species from the following in which one unpaired electron is present, in ____________ .

$N_{2}, O_{2}, C_{2}^{-}, O_{2}^{-}, O_{2}^{2 -}, H_{2}^{+}, {CN}^{-}, {He}_{2}^{+}$ [2024]

Q 4 :
Total number of electrons present in $(π^{*})$ molecular orbitals of $O_{2}, O_{2}^{+}$ and $O_{2}^{-}$ is _________ . [2024]

Q 5 :
When $ψ_{A}$ and $ψ_{B}$ are the wave function of atomic orbitals, then $σ^{*}$ is represented by: [2024]

Q 7 :
Which of the following molecules(s) show/s paramagnetic behavior? [2025]

(A) $O_{2}$
(B) $N_{2}$
(C) $F_{2}$
(D) $S_{2}$
(E) ${Cl}_{2}$

Choose the correct answer from the options given below: