[cappuccino]

I don't really understand what a low-lying vacant orbital is. I get that it has to do with the d orbital and its energy but why does carbon not have it but all other group 14 elements do? Both C and Si don't have any d electrons so how come Si can have it?

[Hunter2]

Its only a model. All elements could have any orbital theoretically, but for some the energy level would be to high to reach them.  So the 2nd. period don't reach them at all.  Also 2n² law of electrons on the outer shell.

[cappuccino]

Also 2n² law of electrons on the outer shell.

What is this law?

[Hunter2]

This means the max. amount of electrons in the outer shell. x = 2n²
n = 1 means x = 2  reached with Helium
n = 2 means x = 8 reached with Neon
n = 3 means x = 18 reached with Zinc
n = 4 means x = 32 reached at Ytterbium
n = 5 means x = 50 not reached

So in Periode 1 and 2 never d orbitals can reached.

[cappuccino]

This means the max. amount of electrons in the outer shell. x = 2n²
n = 1 means x = 2  reached with Helium
n = 2 means x = 8 reached with Neon
n = 3 means x = 18 reached with Zinc
n = 4 means x = 32 reached at Ytterbium
n = 5 means x = 50 not reached

So in Periode 1 and 2 never d orbitals can reached.

Oh right. Thanks