Which of the following is not paramangnetic?

Options

A. `NO`
B. `H_2^(+)`
C. `CO`
D. `O_2`

Answer

C

Explanation

Odd electron species such as `NO(15e^(-)s)` and `N_2^(-)(13e^(-)s)` are always paramagnetic. `O_2` is paramagnetic as it has 2 unpaired electrons in antibonding `MOs`. The electron configuration of `CO` is
`KK(sigma2s)^2(sigma^**2s)^2(pi2p_x^2=pi2p_y^2)(sigma2p_z)^2`
It is diamagnetic as all its electrons are paired.