Question

Which of the following species have maximum number of unpaired electrons?

• A. $O_2$
• B. $O_2^{+}$
• C. $O_2^{-}$
• D. $O_2^{2-}$

Answer 1

Answer: (A)

The electronic configuration of the $O_2$ containing 16 electrons can be written as:

$1s^2\ast 1s^{2}2s^2\ast 2s^{2}2p{z}^{2}2p{x}^{2}2p{y}^2\ast 2p{x}^1\ast 2p{y}^1$

The electronic configuration of the $O_2^{+}$ containing 16 electrons can be written as:

$1s^2\ast 1s^{2}2s^2\ast 2s^{2}2p{z}^{2}2p{x}^{2}2p{y}^2\ast 2p{x}^1\ast 2p{y}^0$

The electronic configuration of the $O_2^{-}$ ion containing 17 electrons can be written as:

$1s^2\ast 1s^{2}2s^2\ast 2s^{2}2p{z}^{2}2p{x}^{2}2p{y}^2\ast 2p{x}^2\ast 2p{y}^1$

The electronic configuration of the $O_2^{-2}$ ion containing 18 electrons can be written as:

$1s^2\ast 1s^{2}2s^2\ast 2s^{2}2p{z}^{2}2p{x}^{2}2p{y}^2\ast 2p{x}^2\ast 2p{y}^2$