Appendix Summary of Quantum Number Characteristics The energy states of electrons are characterized by four quan- tum numbers.The main quantum number,n,determines the overall energy of the electrons,i.e.,essentially the radius of the electron distribution.It can have any integral value.For exam- ple,the electron of a hydrogen atom in its ground state has n=1. The quantum number,l,is a measure of the angular momen- tum L of the electrons and is determined by L=VI(+1), where I can assume any integral value between 0 and n-1. It is common to specify a given energy state by a symbol which utilizes the n-and I-values.States with I=0 are called s-states; with I=1,p-states;and with I=2,d-states,etc.A 4d-state,for example,is one with n=4 and 1=2. The possible orientations of the angular momentum vector with respect to an external magnetic field are again quantized and are given by the magnetic quantum number m.Only m val- ues between +l and-l are permitted. The electrons of an atom fill the available states starting with the lowest state and obeying the Pauli principle which requires that each state can be filled only with two electrons having op- posite spin (s=).Because of the just-mentioned multiplicity, the maximal number of electrons in the s-states is 2,in the p- states 6,in the d-states 10,and in the f-states 14. The electron bands in solids are named by using the same nomenclature as above,i.e.,a 3d-level in the atomic state widens to a 3d-band in a solid.The electron configurations of some iso- lated atoms are listed on the next page.Appendix I The energy states of electrons are characterized by four quan￾tum numbers. The main quantum number, n, determines the overall energy of the electrons, i.e., essentially the radius of the electron distribution. It can have any integral value. For exam￾ple, the electron of a hydrogen atom in its ground state has n
1. The quantum number, l, is a measure of the angular momen￾tum L of the electrons and is determined by L
, where l can assume any integral value between 0 and n  1. It is common to specify a given energy state by a symbol which utilizes the n- and l-values. States with l
0 are called s-states; with l
1, p-states; and with l
2, d-states, etc. A 4d-state, for example, is one with n
4 and l
2. The possible orientations of the angular momentum vector with respect to an external magnetic field are again quantized and are given by the magnetic quantum number m. Only m val￾ues between l and l are permitted. The electrons of an atom fill the available states starting with the lowest state and obeying the Pauli principle which requires that each state can be filled only with two electrons having op￾posite spin (s
* 1 2 ). Because of the just-mentioned multiplicity, the maximal number of electrons in the s-states is 2, in the p￾states 6, in the d-states 10, and in the f-states 14. The electron bands in solids are named by using the same nomenclature as above, i.e., a 3d-level in the atomic state widens to a 3d-band in a solid. The electron configurations of some iso￾lated atoms are listed on the next page. l(l 1)' Summary of Quantum Number Characteristics