Metallic Bonding

a solid sample of a metal

• metal ions packed tightly together into a three-dimensional lattice

• The valence electrons are delocalised and move freely around the lattice.

metallic bonding

The delocalised valence electrons and the metal ions are attracted to each other.

Lustre

The delocalised valence electrons reflect light and scatter it into our eyes, making the material appear shiny.

Conductivity of heat

• Heating a metal gives the delocalised electrons more energy and they vibrate more rapidly. 

• As they come into contact with other delocalised electrons, they transfer the energy, allowing heat to be transmitted quickly.

Conductivity of electricity

• When a metal is connected to a power supply, electrons enter one end of the metal (the negative terminal). The same number of electrons would be attracted towards the positive terminal, this exiting the other end of the metal. 

Malleability & Ductility

• When a metal is bent, its lattice of positive ions is displaced .

• The constant movement of the delocalised electrons prevents the positive ions from getting too close to each other and repel each other, so the metal bends without breaking.

• When a metal is bent, its lattice of positive ions is displaced .

• The constant movement of the delocalised electrons prevents the positive ions from getting too close to each other and repel each other, so the metal bends without breaking.

Hardness & High melting point

This is due to the attractions between the delocalised electrons and the cations being very strong and requiring a lot of energy to break.

High density

• The metal cations can be close together because they are held together by strong attractions to negative electrons. This allows the metal lattice to be tightly packed together.

Properties that cannot be explained by this model

• the range of melting temperatures (some metals are liquids at room temperature), hardness and densities of metals

• the differences in electrical conductivity between metals

• the magnetic nature of metals such as cobalt, iron and nickel

• the different appearances of metals (e.g. why transition metals have colours)

Main Group metals vs Transition Metals

Compared to Groups 1&2 metals, transition metals tend to:

• be harder and more dense (due to having smaller atomic radii than main group metals)

• have higher melting points not be as reactive

Some transition metals also have colours and magnetic properties

Reactivity in Water

• Group 1 metals readily react in water. 

• The amount of heat energy created allows hydrogen gas to be released in these reactions. 

• Transition metals are generally less reactive in water and oxygen. Most react slowly or not at all.

Reactivity in Oxygen

• Group 1 metals react rapidly with oxygen to form metal oxides.

• Group 2 metals also react in oxygen, but not as quickly as group 1

• Transition metals are less reactive with oxygen 

Reactivity in Acids

• Metals are more reactive with acids than oxygen or water. 

• When metals react, their atoms form positive ions by donating one or more of their valence electrons to other atoms 

• Metal atoms that require less energy to remove electrons tend to be most reactive. 

• The most reactive atoms thus are ones with the lowest ionisation energies