We have seen that energy splitting happens when two Hydrogen atoms form a bond. What happens in more complex atoms with more subatomic particles? Let's find out.
Compared to a hydrogen atom, a silicon atom has more sub-atomic particles.
Due to the higher number of electrons, they are able to occupy some higher states.
Interact with the atom to learn more.
The 10 inner electrons are too tightly bound to the nucleolus to interact with other atoms; hence, we only consider the 4 outer electrons that are called valence electrons.
These include the two 3s electrons and the two 3p electrons.
If we consider two isolated atoms, valence electrons are going to occupy the 3S and 3P orbitals as we saw above.
Two orbitals can fuse and form new orbitals (Hybridization). In the case of Si atoms, four new orbitals can be formed via hybridization of the 3S and 3P orbitals. In other words, the wavefunction of an SP3 orbital is a linear function of the wavefunctions of 3S and 3P orbitals.
SP3 orbitals are three dimensional as shown above. For simplicity, we often show them on a 2D plane.
Hover over the electrons to see their orbitals.
When two Si atoms get close and interact, the corresponding energy levels split similar to what we saw for Hydrogen atoms.
Unlike Hydrogen, a Silicon Atom has 3 more electrons after forming one bond. It then looks for three other Silicon Atoms to form bonds. Each new bond results in one energy splitting.
How many electrons are involved in these bonds? Hover over each energy level to see which ones are occupied.
Add more Si atoms to the system and see how additional energy levels appear.
As you add more atoms what happens to the number of electrons in the system? Hover over energy levels to see how many electrons are at each energy state.
A piece of Silicon has a very large number of atoms. Since a bond between every two atoms results in a split, a large number of energy states are created.
Since these energy levels are very tightly packed, they appear almost as if they are continuous bands of energy. However, upon zooming in, we can see that they are an aggregation of discrete energy levels.
Which energy states do you think are occupied and which ones are empty?