Contents
orbital diagram
Molecular orbital diagrams
It is descriptive in nature in view of a covalent bond, where according to this approach, valence electrons influence the stability of the molecule.
The basic principle of this theory is that a number of atomic orbitals join to form the same number of molecular orbitals.
This diagram was introduced in 1928 by Robert S. Milliken; They can explain the existence of certain molecules and the non-existence of others. This scheme is easily adaptable for simple diatomic molecules, such as dioxin and carbon monoxide; Its use becomes complex when it comes to polyatomic molecules which, sometimes, can be relatively simple, as is the case of methane.
On the orbital diagram, what does each square represent?
According to the quantum model, 1 orbital will be the equivalent of a horizontal hairline and each arrow will represent an electron. There can be a maximum of two electrons in each orbital, as their spins are one positive and one negative, the arrows will be placed one up and one down.
If we move on to electromagnetic theory, we will see that when an electron generates an electromagnetic field by spinning a charge, this motion (spin) is what makes the electron behave like a magnet.
The only two possible spins of the electron are one clockwise and one counterclockwise; therefore, it is necessary to add a quantum number when considering its spin, i.e. the spin of the electron will take values of +1/2 or -1/2, in a simple way to put it.
Orbital distribution
For the representation of the distribution of electrons in the orbitals of the different levels, the most useful way and until now used is the one represented symbolically by the notation nlx , where:
- N: represents the main level (in numeric form).
- I: represents the sub-level (symbolized by the letters: S, P, D, F).
- X: total number of electrons presented in this sub-level.
What are the rules for filling orbitals?
There are 3 basic rules:
- Pauli’s Exclusion Principle: states that in no orbital system (atom) two electrons cannot have the same four quantum numbers.
- Aufbau’s principle: states that the orbitals fill progressively, that is to say according to their relative energies, starting with those of lower energy.
- Hund’s rule or maximum multiplicity: says that the spins of the electrons remain unpaired, filling the orbitals with equivalent energy, i.e. if the orbitals are filled so that they are equal, the resulting spin will be the maximum.
Types of orbitals
There are 4 types of orbitals:
- yes
- P
- D
- F
Remember that orbitals are called energy sublevels and can contain different numbers of electrons:
- S=2 electrons.
- P = 6 electrons.
- D = 10 electrons.
- F = 14 electrons.
How to make an orbital diagram?
Once the definition, organization and rules are known, it’s time to practice making an orbital diagram for Oxygen (O), it’s quite easy, so here are the steps:
- We make our Electron configuration, according to the principle of construction, starting from the sub-shells of lower energy, we draw the diagonals; remember that in cases where the atomic number is low, it is not necessary to place all the levels.
In this step, you will need to remember how much space each sublevel takes up; the exponents of the orbitals represent the number of electrons, we proceed:
1s2 2s2 2p4
After making our configuration, we proceed to draw our diagram, for this we will draw small boxes; each orbital will be represented by boxes, for example:
Remember that by Pauli’s exclusion principle, electrons cannot be accommodated with the same spin, so a small arrow is placed up and another in the opposite direction. Having come this far, I must tell you that you have completed your orbital diagram.
