Inner shell of electrons

For the conduction electrons, it is reasonable to consider that the inner-shell electrons are all localized on individual nuclei, in wave functions very much like those they occupy in the free atoms. The potential V should then include the potential due to the positively charged ions, each consisting of a nucleus plus filled inner shells of electrons, and the self-consistent potential (coulomb plus exchange) of the conduction electrons. However, the potential of an ion core must include the effect of exchange or antisymmetry with the inner-shell or core electrons, which means that the conduction-band wave functions must be orthogonal to the core-electron wave functions. This is the basis of the orthogonalized-plane-wave method, which has been successfully used to calculate band structures for many metals.41... 

A further simplication often used in density-functional calculations is the use of pseudopotentials. Most properties of molecules and solids are indeed determined by the valence electrons, i.e., those electrons in outer shells that take part in the bonding between atoms. The core electrons can be removed from the problem by representing the ionic core (i.e., nucleus plus inner shells of electrons) by a pseudopotential. State-of-the-art calculations employ nonlocal, norm-conserving pseudopotentials that are generated from atomic calculations and do not contain any fitting to experiment (Hamann et al., 1979). Such calculations can therefore be called ab initio, or first-principles. ... 

There are two inner shells of electrons that shield the valence electron from the nucleus. 

In an electron dot diagram, the symbol of the element represents the nucleus of the atom plus its inner shells of electrons, and dots around the symbol stand for the valence electrons. The dots are placed arbitrarily to the left or right or above or below the symbol. In unbonded atoms, two dots, at most, are located in each position. For example, atoms of the second period elements may be represented as follows ... 

As mentioned in a footnote to Table 2.1, the use of 8v=l/3 or 8v=4/9 for silicon atoms, as obtained from the definition of 8V (Equation 2.1), causes the overestimation of the effect of the extra inner shell of electrons in silicon atoms on certain physical properties. Whenever this happens, the replacement Si—>C (i.e., 8V=3 or 4) will be made in calculating the valence connectivity indices to correlate that property. For such properties, the differences between Si and C atoms will be taken into account by introducing an atomic correction term for the number of silicon atoms in the repeat unit. The alternative sets of °%v and values obtained for silicon-containing polymers by making the replacement Si—>C in the hydrogen-suppressed graph of the polymeric repeat unit, are listed in Table 2.3. 

It would obviously be convenient to be able to incorporate the fact that the inner shells of electrons are not affected by molecule formation into our computational technique at the outset. In a word it would be extremely useful to be able to simulate the effect of the core electrons on the valence shells. 

Examination of the results of any calculation of the electronic structure of any molecule shows that, where the molecule actually contains atoms with inner shells of electrons, the iimer shells are essentially undisturbed by molecule formation there are always low-lying MOs which are well-separated in energy from the next band of MOs and which are composed almost exclusively of the inner-shell AOs or basis functions of the component atoms of the molecule. 

The atomic permanent magnetic dipole arises from a partly-filled inner shell of electrons, which occurs in the elements of the transition groups. Of these the iron group with incomplete 3d... 

As all electrons are negatively charged, they repel each other. Electrons in full inner shells repel electrons in outer shells. Full inner shells of electrons prevent the full nuclear charge being felt by the outer electrons. This is called shielding. The greater the shielding of outer electrons by the inner electron shells, the lower the attractive forces between the nucleus and the outer electrons. 

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