Metallic properties and bonding

Metallic bonding = The electrostatic attraction between metal cations and a sea of delocalised electrons

metals are found on the left of the periodic table
all metals are found in s-subshells

Property	What this says about the structure
Metals are dense and typically very heavy for their volume	high density
Metals have high melting and boiling points	high melting and boiling points
Metals conduct electricity in both molten and solid state	high electrical conductivity
Metals are good conductors of heat	thermal conductivity
Metals can be shaped and pulled (malleable and ductile)	malleable and ductile

The metallic bonding model

From atoms to metallic bonding

Remember that atoms are unstable if they don’t have a full outer shell and will gain/lose electrons to become full
The dots in the metallic bonding model are not nuclei, but ions (nuclei + inner electron shells)

two generalisations regarding the strength of metallic bonding and the type of metal atom involved can be made:

1. The strength of the metallic bonding in a metal INCREASES with decreasing atomic radius. Explain.

Smaller atoms → smaller ions → smaller distance between positive nucleus of ion and delocaised electrons → stronger electrostatic attraction between metal ions and delocalised electrons → stronger metallic bonding.

2. The strength of the metallic bonding in a metal INCREASES with increasing number of valence electrons that form the sea of electrons. Explain.

More valence electrons → greater charge on cation → stronger electrostatic attraction between metal ions and delocalised electrons → stronger metallic bonding.

Limitations to the model

Although this model of metallic bonding explains many properties, some cannot be explained this way

Properties which can’t be explained include:

Variation of melting points (Mercury melts at -39^oC, Gallium at 30^oC, iron at 1500^oC, Tungsten at 3422^oC)
Different densities, hardness of similar metals
Magnetic nature of iron, nickel, cobalt