Topic 4 – Chemical Bonding & Structure 4.5 – Metallic bonding SWBAT: Explain electrical conductivity and malleability in metals Explain trends in melting point of metals Explain the properties of alloys in terms of non- directional bonding

Metallic Bonding In the elemental state a metal’s outer electrons are held loosely & tend to wander off  delocalized Delocalized electrons are not fixed in 1 position In metals there is an electrostatic attraction b/w the lattice of cations and the delocalized electrons  metallic bonding

Metallic Bonding The strength of the metallic bond is determined by: – The # of delocalized electrons – The charge on the cation – The radius of the cation

Metallic Bonding The greater # of delocalized e - s & the smaller the cation, the greater the binding force b/w them Na: [Ne]3s 1 MP=98°C Mg: [Ne] 3s 2 MP=650°C Strength of metallic bonding tends to decrease down a group as the size of the cation increases Transition elements have very strong metallic bonds due to the large # of e - s that can become delocalized

Metallic Bonding

Alloys Alloys are produced by adding one metal to another metal in the molten state As the mixture solidifies ions of different metals are scattered throughout the lattice Alloys are generally more chemical stable, stronger, and more resistant to corrosion

Alloys steel Stainless steel brass bronze pewter Sterling silver