If every orbital of a lower energy had one electron, and the orbitals of the hext higher energy had none, an electron in this case would occupy the higher energy orbital. On the other hand, when the pairing energy is greater than the crystal field energy, the electrons will occupy all the orbitals first and then pair up, without regard to the energy of the orbitals. Electrons tend to fall in the lowest possible energy state, and since the pairing energy is lower than the crystal field splitting energy, it is more energetically favorable for the electrons to pair up and completely fill up the low energy orbitals until there is no room left at all, and only then begin to fill the high energy orbitals. When the crystal field splitting energy is greater than the pairing energy, electrons will fill up all the lower energy orbitals first and only then pair with electrons in these orbitals before moving to the higher energy orbitals. Normally, these two quantities determine whether a certain field is low spin or high spin. When talking about all the molecular geometries, we compare the crystal field splitting energy (\(\Delta\)) and the pairing energy (\(P\)). One thing to keep in mind is that this energy splitting is different for each molecular geometry because each molecular geometry can hold a different number of ligands and has a different shape to its orbitals.Ī complex can be classified as high spin or low spin. Thus, due to the strong repelling force between the ligand field and the orbital, certain orbitals have higher energies than others. Remember, opposites attract and likes repel. This is because when the orbital of the central atom comes in direct contact with the ligand field, a lot of electron-electron repulsion is present as both the ligand field and the orbital contain electrons. It states that the ligand fields may come in contact with the electron orbitals of the central atom, and those orbitals that come in direct contact with the ligand fields have higher energy than the orbitals that come in indirect contact with the ligand fields. The ligand field theory states that electron-electron repulsion causes the energy splitting between orbitals. The ligand field theory is the main theory used to explain the splitting of the orbitals and the orbital energies in square planar, tetrahderal, and octahedral geometry. The ligand field theory and the splitting of the orbitals helps further explain which orbitals have higher energy and in which order the orbitals should be filled. Finally, the Pauli exclusion principle states that an orbital cannot have two electrons with the same spin. Hunds rule states that all orbitals must be filled with one electron before electron pairing begins. According to the Aufbau principle, orbitals with the lower energy must be filled before the orbitals with the higher energy. When filling orbitals with electrons, a couple of rules must be followed. The s sub-shell has one orbital, the p sub-shell has three orbitals, the d sub-shell has five orbitals, and the f sub-shell has seven orbitals. The sub-shell relates to the s, p, d, and f blocks that the electrons of an observed element are located. Electrons in different singly occupied orbitals of the same sub-shell have the same spins (or parallel spins, which are arrows pointing in the same direction). An arrow pointing up corresponds a spin of +1/2 and an arrow pointing corresponds to a spin of -1/2. When placing electrons in orbital diagrams, electrons are represented by arrows. When these free atoms are doubly ionized, the ionized electrons will come from the $3d$ orbitals because they are higher in energy and the configuration will be [ $\ce$ atoms.\) The first and second ionization energies for cobalt are 760.4 kJ/mol and 1648 kJ/mol, respectively. The radial extent of the $3d$ orbitals is not large compared to the $4s$ orbitals, but the $s$ orbitals have the great advantage of being closer to the nucleus ( $\ell=0$) and therefore always lower in energy compared to the $3d$ orbitals. The ground state of a cobalt atom has $4s$ orbitals for two electrons and five $3d$ orbitals for seven electrons. Let us assume that we have cobalt atoms in the air that do not interact with each other before they form the well known hexagonal solid. There is a difference between unstable free ions that have a small mean free path before getting electrons somewhere and ions due to oxidation states in a compound. This is certainly a misconception and therefore an important question.
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