Model electron sea

The electrons are mobile, however, and no individual electron is confined to any particular metal ion. When a voltage is applied to a metal wire, the electrons, being negatively charged, flow through the metal toward the positively charged end of the wire. 

The high thermal conductivity of metals is also accounted for by the presence of 

The ability of metals to deform (their malleability and ductility) can be explained by the fact that metal atoms form bonds to many neighbors. Chemges in the positions of the atoms brought about in reshaping the metal are partly accommodated by a redistribution of electrons. 

To obtain a more accurate picture of the bonding in metals, we must turn to molecular orbital theory. In Sections 9.7 and 9.8 we learned how molecular orbitals are created from the overlap of atomic orbitals. Let s briefly review some of the rules of molecular orbital theory  

Atomic orbitals combine to make molecular orbitals that can extend over the entire molecule. 

The high thermal conductivity of metals is also accounted for by the presence of mobile electrons. The movement of electrons in response to temperature gradients permits ready transfer of kinetic energy throughout the solid. 

---

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 ...

In Chapter 9, we considered a simple picture of metallic bonding, the electron-sea model The molecular orbital approach leads to a refinement of this model known as band theory. Here, a crystal of a metal is considered to be one huge molecule. Valence electrons of the metal are fed into delocalized molecular orbitals, formed in the usual way from atomic... 

To understand those properties, we need to look at the bonding in metals. We ll consider two theoretical models that are commonly used the electron-sea model and the molecular orbital theory. 

In the electron-sea model, a metal crystal is viewed as a three-dimensional array of metal cations immersed in a sea of delocalized electrons that are free to move throughout the crystal (Figure 21.6). The continuum of delocalized, mobile valence electrons acts as an electrostatic glue that holds the metal cations together. 

The electron-sea model affords a simple qualitative explanation for the electrical and thermal conductivity of metals. Because the electrons are mobile, they are free to move away from a negative electrode and toward a positive electrode when a metal is subjected to an electrical potential. The mobile electrons can also conduct heat by carrying kinetic energy from one part of the crystal to another. Metals are malleable and ductile because the delocalized bonding extends in all... 

FIGURE 21.6 Two- dimensional representation of the electron-sea model of a metal. An ordered array of cations is immersed in a continuous distribution of delocalized, mobile valence electrons. The valence electrons do not belong to any particular metal ion but to the crystal as a whole. 

Two bonding models are used for metals. The electron-sea model pictures a metal as an array of metal cations... 

Describe the electron-sea model of the bonding in cesium metal. Cesium has a body-centered cubic structure. 

How does the electron-sea model account for the malleability and ductility of metals ... 

Cesium metal is very soft, and tungsten metal is very hard. Explain the difference using the electron-sea model. 

Sodium melts at 98°C, and magnesium melts at 649°C. Account for the higher melting point of magnesium using the electron-sea model. 

What properties of metals are better explained by band theory than by the electron-sea model ... 

Tungsten is hard and has a very high melting point (3422°C), and gold is soft and has a relatively low melting point (1064°C). Are these facts in better agreement with the electron-sea model or the MO model (band theory) Explain. 

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. 

Most metals are ductile and malleable, in contrast to the brittleness of most other solids. Account for these properties in terms of the electron-sea model. 

The electron sea model for metals postulates a regular array of cations in a "sea" of valence electrons, (a) Representation of an alkali metal (Group 1A) with one valence electron, (b) Representation of an alkaline earth metal (Group 2A) with two valence electrons. 

The simplest picture that explains these observations is the electron sea model, which envisions a regular array of metal cations in a sea of valence electrons (see Fig. 16.22). The mobile electrons conduct heat and electricity, and the cations are easily moved around as the metal is hammered into a sheet or pulled into a wire. 

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)... 

Figure 4.The electron sea model, (a) represents an alkali metal with one valence electron and (b) represents an alkaline earth metal with two valence electrons. Illustration by Hans Cassidy Courtesy of Gale Group. 

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. 

Formuiating Modeis Draw a model to represent the ductihty of a metal using the electron sea model shown in Figure 8-10. 

The electron sea model can explain the melting point, boiling point, malleability, conductivity, and ductihty of metallic solids. 

The physical properties of metals are attributed to the electron sea model of metallic bonds shown on the right. Metals conduct heat and electricity because electrons are not associated with the bonding between two specific atoms and they are able to flow through the material. They are called delocalized electrons. Metals are lustrous because electrons at their surface reflect light at many different wavelengths. 

A simple model to describe metallic bonds is the so-called electron sea model. Metals can be considered as metal cations surrounded by valence electrons that swim around in all directions like in a sea. In that way, metals have high electrical and thermal conductivity in all directions since the valence electrons freely can move around. In order to describe this in more details we have to introduce the so-called band theory. In the band theory the molecular orbitals (that we heard about in the section 2.2.2 Molecular orbital theory) are again included. 

The bond electrons in covalent bond are very locked in the hybrid orbitals which gives very poor electrical conductance. This is in contrast to the bonds in metals. These bonds can be described by an electron sea model that tells us that the valence electrons freely can move around in the metal structure. The band theory tells us that the valence electrons move around in empty anti-bond orbitals that all lie very close in energy to the bond orbitals. The free movement of electrons in metals explain the very high electrical and thermal conductivity of metals. Metal atoms are arranged in different lattice structures. We saw how knowledge about the lattice structure and atomic radius can lead to calculation of the density of a metal. 

---