Definition and Location
What is a Metallic Bond?: A metallic bond is a special type of bond found only in metals. In this bond, the atoms don’t just connect in simple pairs—instead, all the metal atoms form a large structure where the positive parts (the nuclei) stay in place, and the outermost electrons move freely around them. This is why metals have a shiny appearance and can conduct electricity.
Location in Metals: You will only find metallic bonds in pure metals and metal alloys. In these substances, the metal atoms line up in neat rows and layers to create a regular, repeating pattern known as a lattice. This arrangement helps give metals their strength and flexibility.
Electron Behaviour: The 'Sea of Electrons'
Delocalised Electrons: In a metal, the outer electrons (called valence electrons) don’t belong to just one atom. They are free to move around between all the atoms. This means the electrons are not “locked in” like in other types of bonds.
Electron Sea Model: Scientists call this system the ‘sea of electrons.’ Imagine the metal atoms as positively charged balls sitting in a pool of negatively charged electrons. These electrons can float around freely and help hold the metal together.
Electron Contribution: To form this sea, each metal atom gives away one or more of its outer electrons. The atoms become positively charged particles called cations, and the electrons they released are shared with everyone in the structure.
Formation of the Metallic Bond
Electrostatic Attraction: The metallic bond is formed because the positive metal ions are strongly attracted to the negative sea of electrons. This force of attraction holds everything together in the metal.
Cation Formation: When metal atoms lose their outer electrons, they turn into cations (positively charged ions). These cations are not floating alone—they are held tightly by the sea of free-moving electrons around them.
Non-directional Force: The force between the metal ions and the electrons isn’t pointing in just one direction. It pulls in every direction, which is why the metal structure is very strong and doesn’t break easily when bent or shaped.
Properties Explained by Metallic Bonds
Electrical Conductivity: Because the electrons in the metal can move so easily, they can carry electric current. When you connect a wire to a battery, the electrons flow through the wire, allowing electricity to pass through.
Thermal Conductivity: Not only do these free electrons carry electricity, but they also help pass heat along the metal. That’s why metal pots heat up quickly when placed on a stove—they transfer heat really well.
Malleability and Ductility: Metals can be hammered into sheets (malleable) or pulled into wires (ductile) without breaking. This is possible because the layers of metal ions can slide over one another while still being held together by the electron sea.
High Melting and Boiling Points: It takes a lot of energy to break the strong attraction between the metal ions and the sea of electrons. That’s why metals usually have very high melting and boiling points—they stay solid even at high temperatures.
Visual Representation
Electron Sea Diagram: Rajah 5.30 shows a picture of metal ions packed together with a sea of moving electrons flowing around them. This diagram helps us see how metallic bonding works.
Summary
Key Characteristics: In metallic bonds, electrons from each atom are free to move and form a shared cloud or ‘sea’ around all the atoms. This special bonding holds the metal together.
Resulting Properties: Because of metallic bonding, metals can conduct electricity and heat, be shaped without breaking, and remain solid at high temperatures. These useful properties come from the way electrons move freely among the metal atoms.