Sea of electrons model

The conductivity of metals can also be explained by the sea of electrons model of metallic bonding, as shown in Figure 9.12. Because the valence electrons of all the metal atoms are not attached to any one metal atom, they can move through the metal when an external force, such as that provided by a battery, is applied. 

A semiconductor material such as silicon conducts electricity to a degree. Is the bonding in silicon represented by the sea of electrons model Explain. (Chapter 3)... 

According to the expanded model, each atom in a metallic solid has released one or more electrons, and these electrons move freely throughout the solid. When the atoms lose the electrons, they become cations. The cations form the structure we associate with solids, and the released electrons flow between them like water flows between islands in the ocean. This model, often called the sea of electrons model, can be used to explain some of the definitive characteristics of metals. For example, the freely moving electrons make metallic elements good conductors of electric currents. 

The sea of electrons model provides qualitative understanding, but quantitative models for metallic bonding also exist. The most important such model is band theory, and we can use our example of putting metal atoms into a carbon nanotube to explain the origins of this theory. 

How many electrons per atom are delocalized in the sea of electrons model for the following metals (a) iron, (b) vanadium, (c) silver... 

One important physical property of metals is their malleability. How does the sea of electrons model account for this property ... 

The sea of electrons model is not generally used for quantitative predictions of properties. What factors are left out of this model that might prevent quantitative precision ... 

What is the key difference between metalhc bonding (in the sea of electrons model) and ionic bonding (as described in Chapter 7) that explains why metals conduct electricity and ionic solids do not ... 

To conduct electricity, the material must allow charge to move. In the sea of electrons model, the electrons in the sea can respond to an electric field by moving. So metals conduct electricity. 

Sea-of-electrons model (8.3) Simplified description of metallic bonding in which the valence electrons of metal atoms are delocaUzed and move freely throughout the solid rather than being tied to any specific atom. 

In Pauli s model, we still envisage a core of rigid cations (metal atoms that have lost electrons), surrounded by a sea of electrons. The electrons are treated as non-interacting particles just as in the Drude model, but the analysis is done according to the rules of quantum mechanics. 

In Pauli s model, the sea of electrons, known as the conduction electrons are taken to be non-interacting and so the total wavefunction is just a product of individual one-electron wavefuncdons. The Pauli model takes account of the exclusion principle each conduction electron has spin and so each available spatial quantum state can accommodate a pair of electrons, one of either spin. 

Figure 9.1 Id illustrates a simple model of bonding in metals known as the electron-sea model. The metallic crystal is pictured as an array of positive ions, for example, Na+, Mg2+. These are anchored in position, like buoys in a mobile sea of electrons. These electrons are not attached to any particular positive ion but rather can wander through the crystal. The electron-sea model explains many of the characteristic properties of metals ...

The reader is probably familiar with a simple picture of metallic bonding in which we imagine a lattice of cations M"+ studded in a sea of delocalised electrons, smeared out over the whole crystal. This model can rationalise such properties as malleability and ductility these require that layers of atoms can slide over one another without-undue repulsion. The sea of electrons acts like a lubricating fluid to shield the M"+ ions from each other. In contrast, distortion of an ionic structure will necessarily lead to increased repulsion between ions of like charge while deformation of a molecular crystal disrupts the Van der Waals forces that hold it together. It is also easy to visualise the electrical properties of metals in... 

The electron sea model (see Figure 6.2) for metal bonding proposes a theory that explains observed metal properties. In this model, we can envision that metal bonds are formed when a uniform array of metal cations, positively charged metal ions, are surrounded by a sea of electrons. 

A common alternative is to synthesize approximate state functions by linear combination of algebraic forms that resemble hydrogenic wave functions. Another strategy is to solve one-particle problems on assuming model potentials parametrically related to molecular size. This approach, known as free-electron simulation, is widely used in solid-state and semiconductor physics. It is the quantum-mechanical extension of the classic (1900) Drude model that pictures a metal as a regular array of cations, immersed in a sea of electrons. Another way to deal with problems of chemical interaction is to describe them as quantum effects, presumably too subtle for the ininitiated to ponder. Two prime examples are, the so-called dispersion interaction that explains van der Waals attraction, and Born repulsion, assumed to occur in ionic crystals. Most chemists are in fact sufficiently intimidated by such claims to consider the problem solved, although not understood. 

Experimentally it is observed that specific adsorption occurs more with anions than with cations. This is in agreement with chemical models of the interfacial region. Since, according to the free electron model, a metallic lattice can be considered as a cation lattice in a sea of electrons in free movement, it is logical to expect a greater attraction for anions in solution. 

Electron capture a process in which one of the inner-orbital electrons in an atom is captured by the nucleus. (21.1) Electron sea model a model for metals postulating a regular array of cations in a sea of electrons. (16.4)... 

Instead, in this crowded condition, the outer energy levels of the metal atoms overlap. The electron sea model proposes that all the metal atoms in a metallic solid contribute their valence electrons to form a sea of electrons. The electrons present in the outer energy levels of the bonding metallic atoms are not held by any specific atom and can move easily from one atom to the next. Because they are free to move, they are often referred to as delocalized electrons. When the atom s outer electrons move freely throughout the solid, a metallic cation is formed. Each such ion is bonded to all neighboring metal cations by the sea of valence electrons shown in Figure 8-9. A metallic bond is the attraction of a metallic cation for delocalized electrons. 

---