Chemistry – Physical chemistry | e-Consult

The strength of metallic bonding is determined by the number of delocalised electrons and the number of valence electrons contributed by each metal atom. A higher number of valence electrons per atom leads to a stronger "sea" of electrons and therefore stronger metallic bonding. This, in turn, results in improved electrical and thermal conductivity.

Factors Influencing Strength:

• Number of Valence Electrons: Metals with more valence electrons (e.g., Group 15 and 16 metals) tend to have stronger metallic bonding than those with fewer (e.g., Group 1 and 2 metals).
• Atomic Radius: Larger atomic radius means the valence electrons are further from the nucleus and less strongly held, leading to weaker metallic bonding.
• Crystal Structure: The arrangement of metal atoms in the crystal lattice can also influence the strength of metallic bonding. Close-packed structures generally result in stronger bonding.

Effect of Valence Electrons on Properties:

• Electrical Conductivity: Metals with a high number of delocalised electrons (e.g., copper, silver) are excellent conductors of electricity because the electrons can move freely throughout the metal structure.
• Thermal Conductivity: Similarly, metals with a high number of delocalised electrons are also excellent conductors of heat. The delocalised electrons efficiently transfer thermal energy.
• Malleability and Ductility: Strong metallic bonding allows metal atoms to slide past each other without breaking the bonds, resulting in malleability (ability to be hammered into sheets) and ductility (ability to be drawn into wires).
• Examples: Sodium (Na) has only one valence electron and is a soft, easily malleable metal with low electrical conductivity. Copper (Cu) has four valence electrons and is a strong, ductile metal with excellent electrical conductivity. The difference in the number of valence electrons directly impacts the strength of the metallic bond and, consequently, the metal's properties.