KEY2CHEM

Bonding in Metals

The bonding in metals is described by the “electron sea” model. In this model, delocalized valence electrons surround metal cores (made of metal nuclei plus the inner electrons) in a “sea”; they are not held tightly by any one nucleus. These loosely held electrons explain the characteristics of metals. For example, metals conduct both heat and electricity because the delocalized electrons can disperse the heat more quickly than localized electron pairs; the mobile electrons also conduct charge.

Example 1.

Which substance’s interparticle forces are best modeled by the “electron sea” model?

A. $$\require{mhchem}\ce{CO2}$$

B. $$\require{mhchem}\ce{NaCl}$$

C. $$\require{mhchem}\ce{Cu}$$

Solution

C. $$\require{mhchem}\ce{Cu}$$

Bonding in metals is best described as the “electron sea” model, where loosely held valence electrons are delocalized around metal cores.

Example 2.

Which is not a property of metals?

A. brittle

B. ductile

C. malleable

Solution

A. brittle

Metals can be pulled into wires (ductile) and hammered into sheets (malleable). Because metals can be deformed without cracking, they are not brittle.

Example 3.

Which is not a consequence of the electron sea model of metallic bonding?

A. Metals can be deformed because the electron sea prevents repulsions between metal nuclei.

B. Down a group, melting points decrease because the larger metal ions have a weaker attraction to the electron sea.

C. Across a period, melting points decrease because atomic size increases.

Solution

C. Across a period, melting points decrease because atomic size increases.

Based on the shell model of the atom, melting points increase across a period. The charge on the metal cation increases, which is then more strongly attracted to the electron sea.