Chemical approach based on molecular orbital theory

1 Chemical approach based on molecular orbital theory 

A piece of metal may be regarded as an infinite solid where all the atoms are arranged in a close-packed manner. If a large number of sodium atoms are 

The evolution of a band of molecular orbitals as the number of contributing atoms such as Na increases. The shaded part in the band of N atoms indicates its containing electrons. 

The energy states in a band are not evenly distributed, and the band structure is better described by a plot of energy E against a density of states function N(E) which represents the number of energy states lying between E and SE, as shown in Fig. 4.3.2. 

The number of states within each band is equal to the total number of orbitals contributed by the atoms. For one mole of metal, a s band will consist of No states and a 3p band of 3No states. These bands will remain distinct if the s-p separation is large, as shown in Fig. 4.3.3(a). However, if the s-p separation is small, the s and p bands overlap extensively and band mixing occurs. This situation, as illustrated in Fig. 4.3.3(b), applies to the alkaline-earth metals and main group metals. 

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