(a) Both `N_(2)^(+) and N_(2)^(-)` have same bond order (2.5). Hence both have the same energy.
(b) (i) Both `F_(2),O_(2)^(2-)` are isoelectronic. They have the same molecular orbital configuration as well as the bond ordre.
(ii) CO, `N_(2),NO^(+)` have the same bond order (3.0).
(c ) In Co, thereis multiple bonding present. `(Coverset(larr)(=)O":").` As result, it is quite stable. On the other hand, silicon (Si) atom due to is large size linked to oxygen by single bond only (Si-O). Therefore, it is not so stable.