Lithium atom, electronic states

Each of a lithium atom s three electrons also has its own unique set of quantum numbers, as you can see helow. (Assume these quantum numbers represent a ground state lithium atom.)... 

As an example, for the lowest spin-orbit coupled state for the electronically excited lithium atom (ls 2p 3p ), L, i = 2, S,ou,i = 3/2, and J = 1/2, the term symbol is Pi/2. These are called Russell-Saunders term symbols because it is assumed that the individual orbital angular momentum are more strongly coupled than the spin-orbit coupling. If spin-orbit coupling is ignored, the J term is omitted from the term symbol. 

Some excited configurations of the lithium atom, involving promotion of only the valence electron, are given in Table 7.4, which also lists the states arising from these configurations. Similar states can easily be derived for other alkali metals. 

Liquid gas boundary curves, 87 Lithium atom, ground state of, 313 Lithium hydride, electronic correlation, 324... 

A lithium atom has three electrons. The first two electrons fill lithium s lowest possible energy level, the 1. S orbital, and the third electron occupies the 2 5 orbital. The three representations for the ground-state electron configuration... 

The exclusion principle states that no two electrons in an atom can have the same set of quantum numbers. The Is orbital has the following set of allowable numbers n= 1, f = 0, m = 0, mg = +1/2 or -1/2. All of these numbers can have only one value except for spin, which has two possible states. Thus, the exclusion principle restricts the Is orbital to two electrons with opposite spins. A third electron in the Is orbital would have to have a set of quantum numbers identical to those of one of the electrons already there. Thus, the third electron needed for lithium must go into the next higher energy shell, which is a 2s orbital. 

Consider a crude approximation to the ground state of the lithium atom in which the electron-electron repulsions are neglected. Construct the ground-state wave function in terms of the hydrogen-like atomic orbitals. 

It is well known that the energy profiles of Compton scattered X-rays in solids provide a lot of important information about the electronic structures [1], The application of the Compton scattering method to high pressure has attracted a lot of attention since the extremely intense X-rays was obtained from a synchrotron radiation (SR) source. Lithium with three electrons per atom (one conduction electron and two core electrons) is the most elementary metal available for both theoretical and experimental studies. Until now there have been a lot of works not only at ambient pressure but also at high pressure because its electronic state is approximated by free electron model (FEM) [2, 3]. In the present work we report the result of the measurement of the Compton profile of Li at high pressure and pressure dependence of the Fermi momentum by using SR. 

Figure A.l 1 shows the change in density of states due to chemisorption of Cl and Li. Note that the zero of energy has been chosen at the vacuum level and that all levels below the Fermi level are filled. For lithium, we are looking at the broadened 2s level with an ionization potential in the free atom of 5.4 eV. The density functional calculation tells us that chemisorption has shifted this level above the Fermi level so that it is largely empty. Thus, lithium atoms on jellium are present as Li, with 8 almost equal to 1. Chemisorption of chlorine involves the initially unoccupied 3p level, which has the high electron affinity of 3.8 eV. This level has shifted down in energy upon adsorption and ended up below the Fermi level, where it has become occupied. Hence the charge on the chlorine atom is about-1.

Refer to the sets of quantum numbers for hydrogen and helium that you saw earlier. Then use the quantum numbers for lithium to infer why a lithium atom has the ground state electron configuration that it does. 

In the metallic state, lithium is a very soft metal with a density of 0.534 g/cm. When a small piece is placed on water, it will float as it reacts with the water, releasing hydrogen gas. Lithium s melting point is 179°C, and it has about the same heat capacity as water, with a boiling point of 1,342°C. It is electropositive with an oxidation state of + 1, and it is an excellent conductor of heat and electricity. Its atom is the smallest of the alkali earth metals and thus is the least reactive because its valence electron is in the K shell, which is held closest to its nuclei. 

The weakness of the covalent bond in dilithium is understandable in terms of the low effective nuclear charge, which allows the 2s orbital to be very diffuse. The addition of an electron to the lithium atom is exothermic only to the extent of 59.8 kJ mol-1, which indicates the weakness of the attraction for the extra electron. By comparison, the exother-micity of electron attachment to the fluorine atom is 333 kJ mol-1. The diffuseness of the 2s orbital of lithium is indicated by the large bond length (267 pm) in the dilithium molecule. The metal exists in the form of a body-centred cubic lattice in which the radius of the lithium atoms is 152 pm again a very high value, indicative of the low cohesiveness of the metallic structure. The metallic lattice is preferred to the diatomic molecule as the more stable state of lithium. 

Hydrogen, lithium and other intramolecular bonds or intermolecular ones are by their origin secondary chemical bonds. Strong chemical bonds result from a primary act of interaction of atoms, whereas weak chemical bonds appear as a result of alteration in their valence states on condition that the energy content of valence electrons of those atoms can provide for the formation of new chemical bonds. 

If light is passed through lithium vapor containing lithium atoms in the normal state, with the valence electron in the 2s orbital, the only... 

To account for the magnetic hyperfine interaction in, e.g., the ground state of a lithium atom, it is necessary in the core model to go beyond the usual, restricted Hartree-Fock approximation, which assumes that the spatial parts of one-electron orbitals are independent of mB (the spin-... 

Returning to the lithium atom, it is now clear the Is orbital cannot accommodate all three electrons. Rather, two electrons are in the Is orbital with opposite spins, while the remaining electron is in the 2s orbital with either a or p spin. Hence two determinantal wavefunctions can be written for the ground state of lithium ... 

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