Can somebody explain me what are the vacant 3d orbitals of silicon? Silicon configuration is 1s2 2s2 2p6 3s2 3p2 Where are the d orbitals?

1 Answer
Aug 12, 2018

silicon only has 14 electrons


The reason is that Silicon only has 14 electrons. When you start filling up the orbitals, you do that from the lowest energy and in this order: #"1s" -> "2s" -> "2p" -> "3s" -> "3p" -> "4s" -> "3d"...# . As the levels get larger, their sublevels start to overlap. That's why 4s is at a lower energy than 3d sublevel.

Each sublevel can accommodate a fixed number of electrons depending on the number of orbitals present in the sublevel. Also, 1 orbital can hold a maximum of 2 electrons. Taking that into consideration:

  • s sublevel has 1 orbital, and therefore can hold max 2 electrons
  • p sublevel has 3 orbitals, and can hold max 6 electrons
  • d sublevel has 5 orbitals, and can hold max 10 electrons

When you fill up the orbitals from the lowest energy starting from 1s, you'll notice that all 14 electrons of Silicon are filled up when it reaches 3p.

  • 1s: 2 electrons
  • 2s: 2 electrons
  • 2p: 6 electrons
  • 3s: 2 electrons
  • 3p: 2 electrons
  • Total: 14 electrons

Therefore, 3d orbitals are vacant since Silicon doesn't have that many electrons to reach there.

Scandium will be the first element to fill an electron in 3d sublevel since it has 21 electrons.
#1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1#