Metallic Bonding

Metallic Bonding A metallic bond is the attraction + + + + + Delocalized e- + + + + + AKA Sea of e- + + + + + + + + + + A metallic bond is the attraction of a ________ _______for ____________electrons Metallic cation delocalized

The Electron Sea Electron Sea Model proposes that the nuclei of the metallic cations hold onto their correct ________ of _________, but they may be any valence e- of a neighboring nucleus. number electrons

The Electron Sea They are NOT ______ or _____; like in covalent bonds. Instead, they are floating in a sea above the _______ and can move freely from one atom to the next. shared lost nuclei

delocalized electron = Attractions between positive cations and the negative “sea of e-“ hold the metal atoms together in a lattice. The valence e- of a metal that are free to move easily from one cation to another

Properties of metals med. high melting points high boiling points malleable and ductile heat conductors electrical conductors

Brittleness is typical of ionic substances Brittleness is typical of ionic substances. Imagine what happens to the crystal if a stress is applied which shifts the ion layers slightly. Ions of the same charge are brought side-by-side and so the crystal repels itself to pieces! + + + + + + + + + + + + + + + + + + + +

Malleability of metals Whereas ionic compounds shatter when hit with a mallet (hammer), metallic compounds can be flattened and shaped. Why? The sea of electrons acts as a lubricant. By covering the metal cations, it allows them to slide past each other without repelling. + + + + + + + + +

As the number of increases, increase As the number of increases, increase. In the transition metals, mobile electrons consist of both the electrons (highest s) and the inner electrons. delocalized electrons hardness & strength valence d

Alloy = mixture of metal + another element; not a compound 18 carat Gold Au 75% Ag/Cu 25% Sterling silver Ag 92.5% Cu 7.5% Coinage silver Ag 90% Cu 10% Plumber’s solder Pb 67% Sn 33% Pewter Sn 85% Cu 7.3% Bi 6% Sb 1.7% Brass Cu 60% Zn 39% Sn 1% Steel Fe 99% C 1% Cast Iron Fe 96% C 4% Stainless Steel Fe 80.6% Cr 18% C 0.4% Ni 1%

Types of alloys When two metals with similar size ions are mixed, a alloy is formed examples: substitutional Brass, pewter, 14 carat gold Tin Copper Bronze

When one of the metals’ ions is considerably smaller than the other metal, the smaller ions fill in the small spaces (___________) between the larger ones. This is an __________ _____ example: interstices Interstitial alloy High strength steel interstices Carbon Iron

Summary “Sea of electrons” are reason for a metal’s properties Alloys are mixtures of metals Substitutional alloys have similar sized elements Interstitial alloys have different sized elements Metals are malleable (can be flattened) and ductile (can be drawn into wires), and have luster (are shiny)