Octet rule

[Hanniel U 2B]

Can someone please explain the octet rule and why the first 4 atoms on the periodic table don't have it. Thanks !

[Te Jung Yang 4K]

The octet rule is basically a guideline for bonding which says that elements (with atomic number below 20) should have 4 bonding pairs of electrons (8 e- total - the noble gas configuration).

The first 4 elements do not follow this guideline as they do not need 8 e- to reach a noble gas configuration to feel stable, they can simply have 2 e- to reach the configuration of He.

But be wary, there are exceptions to this guideline that were discussed in class: expanded octet, B and Al, and radicals.

[Hanniel U 2B]

The octet rule is basically a guideline for bonding which says that elements (with atomic number below 20) should have 4 bonding pairs of electrons (8 e- total - the noble gas configuration).

The first 4 elements do not follow this guideline as they do not need 8 e- to reach a noble gas configuration to feel stable, they can simply have 2 e- to reach the configuration of He.

But be wary, there are exceptions to this guideline that were discussed in class: expanded octet, B and Al, and radicals.

Thanks!