The number of antibonding electron pairs in $O_2^{2 - }$ molecular ion on the basis of molecular orbital theory is

In which of the following pairs molecules have bond order three and are isoelectronics

The maximum number of hydrogen bonds formed by a water molecule in ice is

The linear combination of atomic orbitals to form molecular orbitals takes place only when the combining atomic orbitals

$A$. have the same energy

$B$. have the minimum overlap

$C$. have same symmetry about the molecular axis

$D$. have different symmetry about the molecular axis

Choose the most appropriate from the options given below:

In which $O-O$ bond distance is minimum

Identify a molecule which does not exist.