http://www.ck12.org Chapter 8. Ionic and Metallic Bonding
material due to its exposure to the environment is known ascorrosion. Metals like gold and platinum are unusually
resistant to corrosion, which makes them especially valuable for both structural and decorative purposes.
Metals have a wide range of melting points, but most are quite high. Only one metal (mercury) melts below room
temperature. Others (such as gallium) are solid at room temperature but would melt at body temperature, so they
can be melted simply by holding them in your hand. On the other end of the spectrum, tungsten has a melting point
of 3422°C.Figure8.11 shows the melting points of various elements in their most common pure form.
FIGURE 8.11
Melting Points of the Metallic ElementsThe "Sea of Electrons"
The reason metals behave the way they do can largely be explained by the ways that metal atoms bond together
to make a solid material. Pure metals are crystalline solids, but unlike ionic compounds, every point in the crystal
lattice is occupied by an identical atom. The electrons in the outer energy levels of a metal are mobile and capable of
drifting from one metal atom to another. This means that the metal is more properly viewed as an array of positive
ions surrounded by a "sea" of mobile valence electrons (Figure8.12). Electrons that are capable of moving freely
throughout the empty valence orbitals of the metallic crystal are said to be delocalized. Ametallic bondis the
attraction of the stationary metal cations to the surrounding mobile electrons.
FIGURE 8.12
Electron Sea IllustrationThis model for metallic bonding explains some of the physical properties of metals. Metals conduct electricity and