Metallic bonding & alloys + properties

Metallic bond

The strong electrostatic attraction between positively charged ions in a metal and the “sea of mobile (or delocalised) electrons”.zzzzzszzz

Solid metals have their atoms _____ _____ in _____ arrangement.

closely packed, regular

Due to close packing, metal atoms …

“lose” their outermost (valence) electrons and become positively charged ions. these electrons no longer “belong” to any metal atom and are said to be delocalised.

What is the structure of solid metals?

Giant metallic lattice structure

Properties of giant metallic lattice

• Ductile and malleable

• Not soluble in aqueous & organic solvent

• Conduct electricity in solid & molten states

• High melting & boiling points

Hardness of giant metallic lattice structure

Ductile and malleable.

As the “sea” of delocalised electrons in the lattice do not belong to any particular metal ion, if sufficient force is applied to the metal, layers of positive ions can slide over one another without disrupting the metallic bonding.

Electrical conductivity of giant metallic latttice?

Conduct electricity in solid and molten states.

There are mobile electrons to conduct electricity when there is a potential difference applied.

Melting & boiling points of giant metallic lattice lattice

High. Large amount of energy is required to overcome the strong electrostatic forces of attraction between the positive ions and sea of delocalised electrons.

Alloys

A mixture of a metal with one or more other elements

Properties of alloys

• Not as malleable & ductile as metals

• Able to conduct electricity

• Lower melting & boiling points, over a range

Why are alloys’ melting & boiling points over a range and lower?

The presence of other elements in the alloy acts as impurities and thus its melting point is over a range of temperatures.

The difference sizes of atoms in an alloy make the lattice arrangement less regular than a pure metal. This makes the bonds between the atoms weaker and thus lowers the melting point.

Electrical conductivity of alloys?

Able to conduct electricity.

Presence of “sea” of delocalised electrons to act as mobile charge carriers.

Hardness of alloys?

Not as malleable & ductile as metals.

The different sizes of atoms in an alloy disrupt the regular lattice arrangement, hence the layers of atoms cannot slide over each other easily. ffff