why the octet rule in molecules like CO NO and NO2 not followed.. why although no d orbital is present...?

Question

sulphur can form six bonds in H2SO4 and in compounds like these.. because it has an empty d orbital ... but why NO and NO2 exist with three and one non-bonding electrons respectively.. and what is the basis of these nitrogen compounds not to follow the octet rule..... whyyyyy.... please answer me ... cause i can't find it in aaaaany boook .. so i am much confused

Answer 1

Do you want the general chemistry answer or the real answer?
Here's the general chemistry answer:
Because these compounds have an odd number of valence electrons, and since N and O can't exceed 8 electrons, the best that they can do to fill its octet is to have 7. Since oxygen is more electronegative than nitrogen, it's more likely to have its octet filled before nitrogen's, so N gets 7 valence electrons in either compound.

The real answer:
Lewis dot structures are a _model_ for chemical bonding. A model is an explanation for how the world works. Lewis dot structures work as a wonderful model for "ordinary" molecules such as your everyday organic molecules, but they do a poor job in explaining chemical bonding in some compounds. NO and NO2 are two examples in which Lewis dot structures fail to explain the true intricacies of the chemical bonding in these compounds. To really understand chemical bonding in NO and NO2, you'd need to resort to a more sophisticated model, such as molecular orbital (MO) theory.

Answer 2

The octet rule is only a simplification. Any configuration which leads to a lowering of energy is acceptable.