A metallic bond is a type of chemical bond wherein metallic atoms attract each other and stay bonded. The bond’s objective is to attain a low energy state, just like in the case of a covalent bond and ionic bond. Unlike other chemical bonds, a metallic bond is not about a handful of atoms. The electrons move freely within a metallic bond, making it float freely across shells of multiple atoms. In other words, the electrons in a metallic bond are detached from their parent atom at all times.
This phenomenon is referred to as delocalization and which gives the metal tremendous electrical and thermal conductivity, and also structural integrity. Metallic bonds represent a strong network of closely connected atoms, in which the atoms’ valence electrons may overlap, or get into other atom’s energy levels. The atoms do not lose any electrons as they fill the lost ones with other delocalized electrons almost instantly.
Why are Electrons Delocalized in a Metallic Bond?
Generally, metals are low on ionization energy. Low ionization energy means the atom has a larger atomic size and radius. In other words, metal atoms’ valence electrons aren’t held strongly by the nucleus. This also means the energy needed to remove a metal atom’s valence electron is less.
Moreover, the valence shell of a metal atom is invariably partially filled, which makes its valence electrons unstable or more reactive chemically. There emanates the need to have a filled valence shell and the number of electrons a metal typically loses depends on its kind. When the valence electrons leave their parent atoms, the atoms turn into positively charged ions or cations. These cations exist in an environment of negatively charged delocalized or free electrons. Since opposites attract, these positive ions and negative electrons attach, resulting in a metallic bond.
Metallic Bond Strength
A metal is robust due to the strong attraction forces existing between the delocalized electrons and positive nuclei. The free electrons basically function as the adhesive that keep the metal ions attached. Since this adhesive is present in abundance, the metallic bond is quite strong. This strong bond is the reason why metals have high boiling points and melting points.
When a metal is melted, the metallic bond still exists or the bond becomes loose and isn’t broken yet, though the metal may have lost its original shape. The delocalized electrons also make sure the metal doesn’t come apart easily when it’s under duress or hammered. The metallic bond completely breaks only when the metal boils. This is why the boiling point of metal should be considered when determining metallic bond strength.