JEE Main 2019 — Chemistry Inorganic Chemistry

2019mcqmedium

According to molecular orbital theory, which of the following is true with respect to ${\mathrm{Li}}_{2}^{+}$ and ${\mathrm{Li}}_{2}^{-}$ ?

Official previous-year question

Held on 9 Jan 2019 · Verified 6 Jul 2026.

Options

A
$L{i}_{2}^{+}$ is stable and $L{i}_{2}^{-}$ is unstable
B
Both are unstable
C
Both are stable
D
$L{i}_{2}^{+}$ is unstable and $L{i}_{2}^{-}$ is stable

Did you get this right?

Solution

According to molecular orbital theory $L{i}_{2}^{+}$ has 5 electrons $-\sigma 1{s}^{2}{\sigma }^{*}1{s}^{2}\sigma 2{s}^{1}$

$L{i}_{2}^{-}$ has 7 electrons $-\sigma 1{s}^{2} {\sigma }^{*}1{s}^{2} \sigma 2{s}^{2} {\sigma }^{*}2{s}^{1}$

$bond order=\frac{electron in bonding molecular orbital-Electron in Antibonding molecular orbital}{2}$

Bond order of $L{i}_{2}^{+}=\frac{3-2}{2}=\frac{1}{2}$

Bond order of $L{i}_{2}^{-}=\frac{4-3}{2}=\frac{1}{2}$

As both have similar bond order, both $L{i}_{2}^{+}$ and $L{i}_{2}^{-}$ will be stable.

Note: $L{i}_{2}^{-}$ will be relatively unstable to $L{i}_{2}^{+}$ as it has more electrons in anti bonding orbitals, so have more energy and having more repulsion so $L{i}_{2}^{-}$ is less stable as $L{i}_{2}^{+}$

Your note

JEE Main Inorganic Chemistry in other years

Inorganic Chemistry 2026 Inorganic Chemistry 2025 Inorganic Chemistry 2024 Inorganic Chemistry 2023 Inorganic Chemistry 2022 Inorganic Chemistry 2021 Inorganic Chemistry 2020 Inorganic Chemistry 2018 Inorganic Chemistry 2017 Inorganic Chemistry 2016 Inorganic Chemistry 2015 Inorganic Chemistry 2014

Keep practicing Inorganic Chemistry

Work through every JEE Main Inorganic Chemistry PYQ, year by year.

Browse all Chemistry topics

Solution

According to molecular orbital theory $L{i}_{2}^{+}$ has 5 electrons $-\sigma 1{s}^{2}{\sigma }^{*}1{s}^{2}\sigma 2{s}^{1}$

$L{i}_{2}^{-}$ has 7 electrons $-\sigma 1{s}^{2} {\sigma }^{*}1{s}^{2} \sigma 2{s}^{2} {\sigma }^{*}2{s}^{1}$

$bond order=\frac{electron in bonding molecular orbital-Electron in Antibonding molecular orbital}{2}$

Bond order of $L{i}_{2}^{+}=\frac{3-2}{2}=\frac{1}{2}$

Bond order of $L{i}_{2}^{-}=\frac{4-3}{2}=\frac{1}{2}$

As both have similar bond order, both $L{i}_{2}^{+}$ and $L{i}_{2}^{-}$ will be stable.

JEE Main 2019 — Chemistry Inorganic Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Inorganic Chemistry in other years

More JEE Main Inorganic Chemistry questions

Other Chemistry topics for JEE Main

Physical Chemistry

Organic Chemistry

Keep practicing Inorganic Chemistry

JEE Main 2019 — Chemistry Inorganic Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Inorganic Chemistry in other years

More JEE Main Inorganic Chemistry questions

Other Chemistry topics for JEE Main

Physical Chemistry

Organic Chemistry

Keep practicing Inorganic Chemistry