Metallic bonding

Metals have many special properties. They are good at conducting heat. They are good at conducting electric current. They can be bent and shaped, without splitting and almost all metals are heavy and hard, and they can get up to high temperatures without melting. What is it that makes metals so special?

This is to do with how the atoms in metals arrange themselves. All elements consist of atoms. And all atoms are built in a similar way: They have a nucleus in the middle, and electrons around the nucleus. There is a difference however, between metal atoms, and atoms in other elements. Elements that are not metals – non-metals – have atoms that want to get more electrons.

They can get them, by forming bonds between each other. These bonds are made of electrons that are shared between the atoms. The electrons in these bonds stay with the atoms that are bonded together. We say that the electrons are bound, or localised. In metals, it’s exactly the opposite.

Metal atoms want to get rid of some of their electrons. And since all of the atoms want to give away electrons, and none of them wants to take any on, the electrons become free. Free electrons don’t stay with any particular atom, but can travel anywhere throughout the material. We say that these electrons are delocalised. In some kinds of metal, only one electron is released from each atom.

In other metals, two or three electrons from each atom become delocalised. When the atoms release electrons, they become positively charged ions. So all metals consist of positive ions in a “sea” of negative electrons. The negative sea of electrons works like a glue, that binds the positive ions together. This is called metallic bonding.

Metallic bonding can get very strong, pulling the ions close to each other. So this is why most metals are such hard and heavy substances, with high melting points. Now look what happens when we try to change the shape of the metal! As the atoms move around, the sea of electrons follows along with their movement. The electrons adapt to the new shape, and keep holding the ions together.

This is what makes metals malleable. When we heat one side of a metal, the sea of electrons helps the heat spread throughout the material. The heat is transferred quickly by these free-moving electrons, so the entire piece of metal becomes hot. This is what makes metals such good thermal conductors. And if we connect the metal to a source of electricity, such as a battery, all of its free electrons can flow through the metal.

And this is why all metals are good electrical conductors. Metal atoms want to shed some of their electrons. This forms a “sea” of delocalised electrons. And it is this sea of electrons that gives metals their special properties: hardness, malleability, high melting points, good conductivity of heat and of electricity.