JEE MAIN - Chemistry (2022 - 25th July Morning Shift - No. 12)
Among the following species
$$\mathrm{N}_{2}, \mathrm{~N}_{2}^{+}, \mathrm{N}_{2}^{-}, \mathrm{N}_{2}^{2-}, \mathrm{O}_{2}, \mathrm{O}_{2}^{+}, \mathrm{O}_{2}^{-}, \mathrm{O}_{2}^{2-}$$
the number of species showing diamagnesim is _______________.
Answer
2
Explanation
Those species which have unpaired electrons are called paramagnetic species.
And those species which have no unpaired electrons are called diamagnetic species.
(1) $$N_2$$ 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.
(2) Moleculer orbital configuration of $$N_2^{ + }$$ (13 electrons)
= $${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,{\sigma _{2{s^2}}}\,\sigma _{2{s^2}}^ * \,{\pi _{2p_x^2}}\, = \,{\pi _{2p_y^2}}\,{\sigma _{2p_z^1}}$$
Here in $$N_2^{ + }$$, 1 unpaired electron present, so it is paramagnetic.
(3) $$\mathrm{N}_{2}^{2-}$$ has 16 electrons.
Moleculer orbital configuration of $$\mathrm{N}_{2}^{2-}$$ 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 electron present, so it is paramagnetic.
(4) $$\mathrm{N}_{2}^{-}$$ has 15 electrons.
Moleculer orbital configuration of $$\mathrm{N}_{2}^{-}$$ is
$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,\,{\sigma _{2{s^2}}}\,\,\sigma _{2{s^2}}^ * \,\,{\sigma _{2p_z^2}}\,\,{\pi _{2p_x^2}}\,= \,{\pi _{2p_y^2}}\,\pi _{2p_x^1}^ * = \,\,\pi _{2p_y^0}^ * $$
Here 1 unpaired electron present, so it is paramagnetic.
(a) $$O_2^{2−}$$ has 18 electrons.
Moleculer orbital configuration of $$O_2^{2−}$$ is
$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,{\sigma _{2{s^2}}}\,\sigma _{2{s^2}}^ * \,{\sigma _{2p_z^2}}\,{\pi _{2p_x^2}}\, = \,{\pi _{2p_y^2}}\,\pi _{2p_x^2}^ * \, = \,\pi _{2p_y^2}^ * $$
Here is no unpaired electron so it is diamagnetic.
(b) $$O_2^{−}$$ has 17 electrons.
Moleculer orbital configuration of $$O_2^{2−}$$ is
$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,{\sigma _{2{s^2}}}\,\sigma _{2{s^2}}^ * \,{\sigma _{2p_z^2}}\,{\pi _{2p_x^2}}\, = \,{\pi _{2p_y^2}}\,\pi _{2p_x^2}^ * \, = \,\pi _{2p_y^1}^ * $$
Here 1 unpaired electron present, so it is paramagnetic.
(c) $$O_2$$ 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 electron present, so it is paramagnetic.
(d) $$O_2^{+}$$ has 15 electrons.
Moleculer orbital configuration of $$O_2^{+}$$ is
$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,\,{\sigma _{2{s^2}}}\,\,\sigma _{2{s^2}}^ * \,\,{\sigma _{2p_z^2}}\,\,{\pi _{2p_x^2}}\,= \,{\pi _{2p_y^2}}\,\pi _{2p_x^1}^ * = \,\,\pi _{2p_y^0}^ * $$
Here 1 unpaired electron present, so it is paramagnetic.
And those species which have no unpaired electrons are called diamagnetic species.
(1) $$N_2$$ 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.
(2) Moleculer orbital configuration of $$N_2^{ + }$$ (13 electrons)
= $${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,{\sigma _{2{s^2}}}\,\sigma _{2{s^2}}^ * \,{\pi _{2p_x^2}}\, = \,{\pi _{2p_y^2}}\,{\sigma _{2p_z^1}}$$
Here in $$N_2^{ + }$$, 1 unpaired electron present, so it is paramagnetic.
(3) $$\mathrm{N}_{2}^{2-}$$ has 16 electrons.
Moleculer orbital configuration of $$\mathrm{N}_{2}^{2-}$$ 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 electron present, so it is paramagnetic.
(4) $$\mathrm{N}_{2}^{-}$$ has 15 electrons.
Moleculer orbital configuration of $$\mathrm{N}_{2}^{-}$$ is
$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,\,{\sigma _{2{s^2}}}\,\,\sigma _{2{s^2}}^ * \,\,{\sigma _{2p_z^2}}\,\,{\pi _{2p_x^2}}\,= \,{\pi _{2p_y^2}}\,\pi _{2p_x^1}^ * = \,\,\pi _{2p_y^0}^ * $$
Here 1 unpaired electron present, so it is paramagnetic.
(a) $$O_2^{2−}$$ has 18 electrons.
Moleculer orbital configuration of $$O_2^{2−}$$ is
$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,{\sigma _{2{s^2}}}\,\sigma _{2{s^2}}^ * \,{\sigma _{2p_z^2}}\,{\pi _{2p_x^2}}\, = \,{\pi _{2p_y^2}}\,\pi _{2p_x^2}^ * \, = \,\pi _{2p_y^2}^ * $$
Here is no unpaired electron so it is diamagnetic.
(b) $$O_2^{−}$$ has 17 electrons.
Moleculer orbital configuration of $$O_2^{2−}$$ is
$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,{\sigma _{2{s^2}}}\,\sigma _{2{s^2}}^ * \,{\sigma _{2p_z^2}}\,{\pi _{2p_x^2}}\, = \,{\pi _{2p_y^2}}\,\pi _{2p_x^2}^ * \, = \,\pi _{2p_y^1}^ * $$
Here 1 unpaired electron present, so it is paramagnetic.
(c) $$O_2$$ 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 electron present, so it is paramagnetic.
(d) $$O_2^{+}$$ has 15 electrons.
Moleculer orbital configuration of $$O_2^{+}$$ is
$${\sigma _{1{s^2}}}\,\sigma _{1{s^2}}^ * \,\,{\sigma _{2{s^2}}}\,\,\sigma _{2{s^2}}^ * \,\,{\sigma _{2p_z^2}}\,\,{\pi _{2p_x^2}}\,= \,{\pi _{2p_y^2}}\,\pi _{2p_x^1}^ * = \,\,\pi _{2p_y^0}^ * $$
Here 1 unpaired electron present, so it is paramagnetic.
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