Electron configuration, determination

Q Write the electronic configurations for the elements hydrogen through neon. Explain how electronic configurations determine the electronegativities and bonding properties of these elements, and how the third row elements (e.g., Si, P, and S) differ from them. 

Fig. 42.9 Mnemonic for electronic configuration determination based on the Aufbau principle.

Given each of the following valence electron configurations, determine which block of the periodic table the element is in. 

Explain how an atom s valence electron configuration determines its place on the periodic table. (6.2)... 

The standard term symbol gives a pre-superscript of 2S 11, where S is the total spin. The major symbol is the total angular momentum. The post-superscript and subscript are a symmetry term and a spin orbital coupling term. The electronic configuration determines the term symbol. 

Electron configuration determines the properties of an element. The modem periodic table classifies the elements according to their atomic numbers, and thus also by their electron configurations. The configuration of the valence electrons directly affects the properties of the atoms of the representative elements. 

The universe is made up of elements that in turn consist of neutrons, protons, and electrons. There are roughly 100 elements, each possessing a unique electronic configuration determined by its atomic number Z, and the spatial distribution and energies of their electrons. What determines the latter requires some understanding of quantum mechanics and is discussed in greater detail in the next chapter. 

X-ray photoelectron spectroscopy (XPS) is a nondestructive quantitative spectroscopic analysis approach that measures the elemental composition, empirical formula, chemical state and electron state of the elements existing within the surface of a material. The principle behind this technique is the photoelectric effect. By calculating the binding energy, a characteristic of the electron configuration, determined as the attraction of the electrons to the nucleus, the number of electrons detected (sometimes per unit time) is plotted correspondingly in a typical XPS spectrum. 

To write electron configurations, determine the number of electrons in the atom from the element s atomic number and then follow these rules ... 

Most elements do not exist as pure elements in nature. Instead, they bond together to form compounds (5.1). An element s electron configuration determines its chemical reactivity-those elements having full outer Bohr orbits are most stable (5.2). Most elements do not have full outer orbits therefore, they exchange or share electrons with other elements to obtain a stable configuration. If the electrons are transferred, as between a metal and a nonmetal, the resulting bond is called an ionic bond (5.3). If the electrons are shared, as between two nonmetals, the resulting bond is called a covalent bond (5.4). 

FIGURE 4.22 On the left, the mnemonic device for determining the order with which energy sublevels fill with electrons. On the right are some examples of electron configuration determined using this device. 

The following Example Problem illustrates how electron configuration determines an element s position in the periodic table. 

In practice, each CSF is a Slater determinant of molecular orbitals, which are divided into three types inactive (doubly occupied), virtual (unoccupied), and active (variable occupancy). The active orbitals are used to build up the various CSFs, and so introduce flexibility into the wave function by including configurations that can describe different situations. Approximate electronic-state wave functions are then provided by the eigenfunctions of the electronic Flamiltonian in the CSF basis. This contrasts to standard FIF theory in which only a single determinant is used, without active orbitals. The use of CSFs, gives the MCSCF wave function a structure that can be interpreted using chemical pictures of electronic configurations [229]. An interpretation in terms of valence bond sti uctures has also been developed, which is very useful for description of a chemical process (see the appendix in [230] and references cited therein). 

These elecironic configuraiions are formal ihe orbitals in these heavy atoms are so close in energy that actual electronic configurations are very difficult to determine. 

The normalisation factor is assumed. It is often convenient to indicate the spin of each electron in the determinant this is done by writing a bar when the spin part is P (spin down) a function without a bar indicates an a spin (spin up). Thus, the following are all commonly used ways to write the Slater determinantal wavefunction for the beryllium atom (which has the electronic configuration ls 2s ) ... 

Structure determines properties and the properties of atoms depend on atomic struc ture All of an element s protons are m its nucleus but the element s electrons are dis tributed among orbitals of varying energy and distance from the nucleus More than any thing else we look at its electron configuration when we wish to understand how an element behaves The next section illustrates this with a brief review of ionic bonding... 

For some systems a single determinant (SCFcalculation) is insufficient to describe the electronic wave function. For example, square cyclobutadiene and twisted ethylene require at least two configurations to describe their ground states. To allow several configurations to be used, a multi-electron configuration interaction technique has been implemented in HyperChem. 

Chemical appHcations of Mn ssbauer spectroscopy are broad (291—293) determination of electron configurations and assignment of oxidation states in stmctural chemistry polymer properties studies of surface chemistry, corrosion, and catalysis and metal-atom bonding in biochemical systems. There are also important appHcations to materials science and metallurgy (294,295) (see Surface and interface analysis). 

In coating fullerenes with alkali metals, the stability of the cluster seemed to be determined primarily by the electronic configuration. The units C qM and C7oMg, where M is any alkali metal, proved to be exceptionally stable cluster building blocks. Coating a fullerene with more than 7 alkali metal atoms led to an even-odd alternation in the mass spectra, inter-... 

The electronic configurations of the free atoms are determined only with difficulty because of the complexity of their atomic spectra, but it is generally agreed that they are nearly all [Xe]4f 5d 6s. The exceptions are ... 

So, we have learned that a single Slater determinant can adequately describe some electronic configurations, but others can only be described by a linear combination of Slater determinants, even at the lowest level of accuracy. 

Here the a, are the LCAO coefficients, which have to be determined. The formulation of HF theory where we use the LCAO approximation is usually attributed to Roothaan (1951a). His formulation applies only to electronic configurations of the type 1/ 3,...,. Following the discussion of Chapter 5, the charge... 

Aufbau principle (Section 1.3) The rules for determining the electron configuration of an atom. 

Perhaps the most obvious metallic property is reflectivity or luster. With few exceptions (gold, copper, bismuth, manganese) all metals have a silvery white color which results from reflecting all frequencies of light. We have said previously that the electron configuration of a substance determines the way in which it interacts with light. Apparently the characteristic reflectivity of metals indicates that all metals have a special type of electron configuration in common. 

A primary goal of the periodic table is to assist recognition of the ground-state valence electron configuration of each atom, the chief determinant of its chemical properties" ([21], p 5). 

The number of energy levels found to date, with the aid of the Zeeman effect and the isotope shift data, is 605 even and 586 odd levels for Pu I and 252 even and 746 odd for Pu II. The quantum number J has been determined for all these levels, the Lande g-factor for most of them, and the isotope shift for almost all of the Pu I levels and for half of those of Pu II. Over 31000 lines have been observed of which 52% have been classified as transitions between pairs of the above levels. These represent 23 distinct electron configurations. 

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