Expalin
(a) `H_(2)^(o+)` and `H_(2)^(Θ)` ions have same bond order but `H_(2)^(o+)` ions are more stable than `H_(2)^(Θ)`
(b) It is possible to have a diatomic molecule with its ground sate `MO` s full with electrons
(c ) Why `2p_(x0` or `2p_(y)` orbitals do not combine with 2s orbitals to form `MO` (Taking Z-axis as the internuclear axis) .

Explanation

`MO` Electronic configuration of `H_(2)^(o+)(Z =1) = sigma 1s^(1)`
`MO` Electronic configuration of `H_(2)^(Θ) (Z =1) sigma 1s^(2),overset(**)sigma 1s^(1)`
`H_(2)^(o+)` ion is more stable due to the presence of one electron in bonding `MO` But `H_(2)^(Θ)` is less stable due to the presence of one electron in the antibonding `overset(**)sigma 1s` `MO` due to which there is some destabilising effect
(b) `NO` Because in such case `BO` becomes zero for example in case of `He_(2),Be_(2),Ne_(2)etc`
Note In `H_(2),BO` is one `sigma 1s MO` is full while `overset(**)1s` antibonding `MO` is empty
(c ) Small `(+)(+)` overlap cancels the `(+)(-)` overlap Hence there is no net overlapping .