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JEE Mains Previous Years Questions with Solutions

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JEE Main 2013 (Offline)

MCQ (More than One Correct Answer)
Which one of the following molecules is expected to exhibit diamagnetic behaviour?
A
N2
B
O2
C
S2
D
C2

Explanation

Those species which have unpaired electrons are called paramagnetic species.

And those species which have no unpaired electrons are called diamagnetic species.

(A)   $$N_2$$ has 14 electrons.

Moleculer orbital configuration of $$N_2$$

= $${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,{\sigma _{2{s^2}}}\,\sigma _{2{s^2}}^ * \,{\pi _{2p_x^2}}\, = \,{\pi _{2p_y^2}}\,{\sigma _{2p_z^2}}$$

Here no unpaired electron present, so it is diamagnetic.

(B)   $$O_2$$ has 16 electrons.

Moleculer orbital configuration of $$O_2$$ is

$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,\,{\sigma _{2{s^2}}}\,\,\sigma _{2{s^2}}^ * \,\,{\sigma _{2p_z^2}}\,\,{\pi _{2p_x^2}}\,= \,{\pi _{2p_y^2}}\,\pi _{2p_x^1}^ * = \,\,\pi _{2p_y^1}^ * $$

Here 2 unpaired electrons present, so it is paramagnetic.

(C)    $$S_2$$ has 32 electrons.

It also has 2 unpaired electrons like $$O_2$$, so it is paramagnetic.

(D)   $$C_2$$ has 12 electrons.

Moleculer orbital configuration of $$C_2$$

= $${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,{\sigma _{2{s^2}}}\,\sigma _{2{s^2}}^ * \,{\pi _{2p_x^2}}\, = \,{\pi _{2p_y^2}}$$

Here no unpaired electron present, so it is diamagnetic.

Questions Asked from Chemical Bonding & Molecular Structure

On those following papers in MCQ (Multiple Correct Answer)
Number in Brackets after Paper Indicates No. of Questions
JEE Main 2013 (Offline) (1)
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