Molecular Quantumness

Electron Orbitals... some more details.

Orbitals have many different shapes and regions. They are presented below in the form of a 3d representation and in a regional density type distribution.

Let's say we take a carbon atom. It has 6 electrons, and each electron occupies some space around the atom. The first and second electrons will fill the 1s orbital. This orbital is an s orbital, where the electron occupies a spherical area with a probability of being in each part of the sphere. Notice in the picture how the density of the 1s orbital is the closest to the nucleus. The closeness of the negatively charged electron and positively charged nuclei reduces the potential energy in the system (note the kinetic energy of the electron in this orbital is higher). Note that electrons like being in an overall lower energy state.

After, the 3rd and 4th electron will occupy the higher energy 2s orbital (in the second energy level - this is called the second quantum principle number). After this, the 5th electron will have to go to higher energy level, to the regions of space called the p orbitals.

These p orbital structures contain "nodes". Nodes are found in many types of orbitals including p orbitals and higher energy s orbitals. Nodes are areas within the electron probability distribution that harbour a probability of 0 in relation to an electron being in such a position.

The 5th and 6th electron will then occupy the p orbitals. But they don't occupy the same p orbital! As in the diagram below , there are 3 p orbitals, each oriented differently (in the x, y and z plane). The electrons prefer to occupy each type of orbital separarely (for example, each prefer to occupy each type of p orbital. But for s orbitals, both electrons have to go in the same orbital as there is only 1 for each particular quantum principle number). This is because electrons repel when they are in the same orbital which is less stable.

So carbon is often denoted as having an electron configuration of

• 2 electrons occupying a 1s orbital
• 2 electrons occupying a 2s orbital
• One electron occupying one orientation of a 2p orbital, and the other electron occupying another orientation of a 2p orbital.