Learn why metallic bonding is called the electron sea model. Discover why metals bond the way they do and why they are shiny, malleable and conduct electricity well.
Electron Sea Model
Metals make up most of the elements in the periodic table (around 80%), and they are special.
When metals bond with themselves, they bond in a different way than when they bond with other elements. It isn’t ionic or molecular or covalent. It is its own metal bond.
Most metals have very few electrons in their outermost energy shells, and some have vacant outer electron orbitals. What this means for the metal is that its valence electrons are decentralized and free to move around. Remember that in ionic bonds, the electrons transfer from one atom to another atom.
In covalent bonds, the electrons are shared between atoms. In metal bonds, the electrons wander around and aren’t transferred or shared. It’s more of a communal thing where they belong to all the metal atoms around them.
Metals form compact and orderly crystalline structures. They look like this:
When metals are next to each other, the valence electrons don’t just stay on their own atom; they roam around the whole metal complex. They float free as though floating through a sea of electrons, much like an individual water molecule floats free in the sea. This is why it is called the electron sea model.
Each metal atom allows its electrons to roam freely, so these atoms become positively charged cations. These cations are kind of like a positively charged island and are surrounded by a sea of negatively charged electrons. It looks a bit like this:
The attraction between the mobile electrons and positive centers is a metal bond.
Properties of Metals
The electron sea model explains many of the physical properties of metals. They are good electrical conductors because the electrons flow freely in them.
They are malleable because of the drifting electrons and because the cations slide easily past each other. They reflect light because of the free electrons.Electricity is the flow of electric charge. Electric charge is a physical property. It comes in two forms – positive and negative – that repel each other.
It starts with the subatomic particles, electrons and protons. What we think of as electricity, which is actually called electric current, is when those electrons move from one place to another. The reason that metals are so good at conducting electricity is that they have all those mobile electrons.
Since those electrons are so free and unencumbered, they can readily move when attracted by a positive charge.
Electrons are also very malleable, which means they can be shaped or formed. Since metals form those nice crystalline structures and they are made up of all those positive centers and negative electrons, the bonding in them is the same in all directions.
Metal atoms can move over each other without breaking or causing any harm to the crystalline structure. This is sort of like a bunch of ball bearings covered in oil. They can roll on past each other easily without damage.Metals are shiny because they reflect light.
Reflection happens when a photon of light hits a surface and changes direction to come back in the direction it originated. Metals reflect light because when the photon of light hits the free electrons in the metal, they cause the photon to change direction and be reflected back where it came from instead of being absorbed.
Metals form bonds that are different from the ionic, covalent and molecular bonds you’ve learned about before. In metals bonds, the electrons move freely around in an electron sea, and this leads to metals’ unique properties. Metal is shiny because it reflects incoming light photons.
It is malleable because the structure and uniform bonding in all directions of the metal allow the atoms to slide past each other without breaking. Metal conducts electricity well because all of the mobile electrons are free to move towards any attraction.
At the conclusion of this lesson, you’ll be able to:
- Describe metallic bonding and the electron sea model
- Explain the unique properties of metals and how they relate to the electron sea model