Question

There are exceptions to the Octet rule. State the exceptions and give samples to them.

Answer 1

There are three ways in which octet rule can break:

1. Odd number of electrons:

Molecule NO has nitrogen with 5 electrons in its octet is there is a single bond between N and O. There will be 7 electrons is there will be a double bond and 9 electrons if there will be a triple bond between N and O. So, in any case there are odd number of electrons in Nitrogen's octet.

2. Electrons less than Octet:

In BF3, even after bonded to three flourine atoms, boron has only 6 electrons in its valence shell i.e less than an octet.

3. More than an octet:

PCl5 is a stable compound, in which P is bonded to five Cl atoms. After bonding phosphorus has 10 electrons in its valence shell i.e more than an octet.

So, in such cases octet rule breaks.