According to the molecular orbital theory, the bond order in ${C_2}$ molecule is
$0$
$1$
$2$
$3$
The bond order in $N_2^ + $ ion is
The bond order is maximum in
In which of the following process, the value of bond order & magnetic nature does not change?
Oxygen molecule is paramagnetic because
Which one of the following species does not exist under normal conditions ?