Chemical properties electron shell configurations

In chemical education, the main motivation for basing chemistry on electronic configurations seems to be that if one knows the number of outer shell electrons in any particular atom, one can predict its chemical properties (Cotton and Wilkinson [1966], Kotz and Purcell [1987]). 

Figure 5. Niels Bohr came up with the idea that the energy of orbiting electrons would be in discrete amounts, or quanta. This enabled him to successfully describe the hydrogen atom, with its single electron, In developing the remainder of his first table of electron configurations, however, Bohr clearly relied on chemical properties, rather than quantum theory, to assign electrons to shells. In this segment of his configuration table, one can see that Bohr adjusted the number of electrons in nitrogen s inner shell in order to make the outer shell, or the reactive shell, reflect the element s known trivalency.

The charge on the nucleus and the number of electrons in the valence shell determine the chemical properties of the atom. The electron configurations of the noble gases (except for that of helium) correspond to a valence shell containing eight electrons—a very stable configuration called an... 

The configuration of electrons around the nuclei of atoms is related to the structure of the periodic table. Chemical properties of elements are mainly determined by the arrangement of electrons in the outermost valence shells of atoms. (Other factors also influence chemical... 

The physical and chemical properties of an atom are determined by the number and configuration of electrons in its electronic retinue. These are arranged in layers or shells, in a well-defined order. Some atoms have more shells than others, or indeed their shells are more complete and better organised. Chemical properties and molecule formation are determined by the outer shell. This is because only the outer electrons can mediate in chemical bonds, playing the role of a common currency. Atoms in the first column of Mendeleyev s periodic table have a single electron in their outermost shell, whilst those in the second column have two, and so on, until we reach the noble gases which have eight electrons in their outer layer (except for helium, which has two). 

The chemical properties of atoms and the types of bond they form with each other are determined by their electron shells. The electron configurations of the elements are therefore also shown in Fig. A. Fig. B explains the symbols and abbreviations used. More de-... 

Electron configuration of an atom indicates its extranuclear structure that is, arrangement of electrons in shells and subshells. Chemical properties of elements (their valence states and reactivity) can be predicted from electron configuration. 

We need to pay particular attention to the valence-shell electrons because they affect the chemical properties most directly. Each element in one of the main groups has a characteristic electron configuration shared by its congeners. As well as electron configurations, which control the valence of the element (the number of bonds it can form), there are five main atomic properties to keep in mind atomic radius, ionization energy, electron affinity, electronegativity, and polarizability. 

Although rare-earth ions are mosdy trivalent, lanthanides can exist in the divalent or tetravalent state when the electronic configuration is dose to the stable empty, half-filled, or completely filled shells. Thus samarium, europium, thulium, and ytterbium can exist as divalent cations in certain environments. On the other hand, tetravalent cerium, praseodymium, and terbium are found, even as oxides where trivalent and tetravalent states often coexist. The stabilization of the different valence states for particular rare earths is sometimes used for separation from the other trivalent lanthanides. The chemicals properties of the di- and tetravalent ions are significantly different. 

The physical and chemical properties of the elements are directly related to their electron configurations. For example, chemical properties such as gaining, giving and sharing of electrons are dependent on the valence electrons and nucleus structure. As a result, chemical behaviors of the elements are closely related to the nucleus structure and electron configuration of the element. Elements in the same period contain different numbers of electrons in the valence shells. 

Three places after xenon there follows the remarkable group of the elements of the Rare Earths, because here, beginning with cerium, the Nf or 4f shell (/ — 3, m = —3, —2, —1, o, 1, 2, 3) is filled up. There is thus produced a group of 14 elements from cerium (58) to lutecium (71), which all possess the same electron configuration of the outermost shell as lanthanum and thus also show a great similarity in chemical properties [group of the lanthanides or lanthanons]. 

The elements display a periodicity of electronic conf uration. For example, if we examine the detailed electronic configurations of the alkali metals, we find that the outermost shell (specifically, the s subshell) of electrons contains only a single electron in each case. The alkahne earth metals have two outermost electrons. The elements within each other group of the periodic table also have similarities in their outermost electronic configurations. We deduce that the outermost part of the electronic configuration is the main factor that determines the chemical properties of the elements because the periodic table was constructed from data about the properties of the elements. 

The elements with atomic numbers from 57 (l thanum) to 71 (lutetium) are referred to as the lanthanide elements. These elements and two others, scandium and yttrium, exhibit chemical and physical properties very similar to lanthanum. They are known as the rare earth elements or rare earths (RE). Such similarity of the RE elements is due to the configuration of their outer electron shells. It is well known that the chemical and physical properties of an element depend primarily on the structure of its outermost electron shells. For RE elements with increasing atomic number, the first electron orbit beyond the closed [Xe] shell (65 remains essentially in place while electrons are added to the inner 4f orbital. Such disposition of electrons about the nucleus of the rare earth atoms is responsible for the small effect an atomic number increase from 57 to 71 has on the physical and chemical properties of the rare earths. Their assignment to the 4f orbital leads to slow contraction of rare earth size with increasing atomic number. The 4f orbitals of both europium and gadolinium are half occupied [Xe] (4F6s and [Xe] (4F5d 6s, so that there... 

It is assumed that the use of the Periodic Table as a basis of study of the properties of the elements is understood. Its value for this purpose stems from the fact that atoms with similar electron configurations lie in the same columns. For example, excluding completely filled inner shells, the configurations of the atoms C, Si, Ge, Sn, Pb are 2p, 3p2, 4p2, 5p and Gp respectively all the elements have the same spectroscopic ground state as carbon, namely P, and the similarity of their outermost structure is responsible for a family relationship in chemical properties. 

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