Atoms with 8+ valence e-

[Miriam Sheetz 2B]

Why can some atoms have more than an octet for their Lewis structure? I know it has something to do with the period they are in but I am still confused about it.

[taline_n]

Elements in the 3rd period and below can have more than an octet because they can access their d orbital electrons, while other elements without d orbital electrons (in period 2, such as C,N,O) cannot, therefore restricting them to only having 8 electrons.

[Seohyun Park 1L]

The elements that can have more than 8 valence electrons have orbitals principal quantum number of at least 3 (n=3) so they have access to the d orbitals (d orbitals only start appearing from n=3). So, they can put the extra electrons in the d orbital. This explains why oxygen and nitrogen are not able to have more than 8 valence electrons since they don't have access to the d orbitals (n=2) while sulfur, a period down, does.

[yaosamantha4F]

The energy between the 3d and 4s orbitals is not very big, so the d-orbitals can take in additional e- to give an expanded octet. In the first and second periods of the periodic table, no d-orbital exists, but starting with the third period, the d-orbital is present and can accomodate additional e-.

[Erin Nash - 4G]

Atoms that are in the 4th period and below are the ones that are able to exceed the octet rule because they have access to their 3d orbitals. The energy difference between the 3d and 4s orbital is much smaller in comparison to other orbitals.

[Katie_Duong_1D]

Atoms in period 3 and greater can have an expanded octet (more than 8 valence electrons) because they also have d and f sub shells, so the can accommodate more than 8 electrons.

[Elizabeth Kim 4E]

D and f subshells can account for more than 8 electrons, therefore the expanded octet.