Building-up principle

Because of the LCAO-MO approximation, ah iniiio and semi-empirical calculation s produce occupied and unoccupied (viriual) orbitals. The Aufban or building up" principle determines the... 

The procedure that we have been using is called the building-up principle. It can be summarized by two rules. To predict the ground-state configuration of a neutral atom of an element with atomic number Z with its Z electrons ... 

The building-up principle is also commonly called the Aufbmt principle, from the German word for building up. ... 

We account for the ground-state electron configuration of an atom by using the building-up principle in conjunction with Fig. 1.41, the Pauli exclusion principle, and Hund s rule. 

The ground-state electron configurations tor Cr and Cu are not those predicted by the building-up principle. Give their actual electron configurations and explain what causes them to deviate from the expected configuration. 

In the heavier transition-metal elements, especially the lanthanoids and actinoids, there are numerous exceptions to the regular order of orbital occupation predicted by the building-up principle. Suggest why more exceptions would be noted for these elements. 

In the molecular orbital description of homonuclear diatomic molecules, we first build all possible molecular orbitals from the available valence-shell atomic orbitals. Then we accommodate the valence electrons in molecular orbitals by using the same procedure we used in the building-up principle for atoms (Section 1.13). That is,... 

When N valence atomic orbitals overlap, they form N molecular orbitals. The ground-state electron configuration of a molecule is deduced by using the building-up principle to accommodate all the valence electrons in the available molecular orbitals. The bond order is the net number of bonds that hold the molecule together. 

Step 3 Note the total number of electrons present in the valence shells of the two atoms. If the species is an ion, adjust the number of electrons to account for the charge. Step.4 Accommodate the electrons in the molecular orbitals according to the building-up principle. 

The ground-state electron configurations of diatomic molecules are deduced by forming molecular orbitals from all the valence-sbell atomic orbitals of the two atoms and adding the valence electrons to the molecular orbitals in order of increasing energy, in accord ivith the building-up principle. 

Suggest the form that the orbital energy-level diagram would take for a square planar complex with the ligands in the xy plane, and discuss how the building-up principle applies. Hint The d -orbital has more electron density in the xy plane than the dzx- or d -orbitals but less than the dXJ,-orbital. 

Aufbau principle See building-up principle. autoionization See autoprotolysis. autoprotolysis A reaction in which a proton is transferred between two molecules of the same substance. The products are the conjugate acid and conjugate base of the substance. Example ... 

The electronic configurations of isolated atoms, up to Z = 36, can be predicted using the building-up principle. There are three important rules to follow ... 

Be able to write both the energy-level diagram and the electronic configuration of an atom or ion by applying both the Aufbau build-up principle and Hund s rule. 

The Aujbau (building up) Principle. One-electron orbitals are filled (occupied) by electrons sequentially, in the order of increasing energy. 

The Aufbau or build-up principle states that electrons occupy orbitals of progressively increasing energies. 

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