Metallic Bonding: Definition, Types, & Properties

All the matters are made up of atoms. Metallic Bonding is a force that binds atoms in a metallic substance together. The atoms that the electrons leave behind become positive ions, and their interaction with valence electrons produces the cohesive or binding force that binds the metallic crystal together. The attractive force which holds together atoms, molecules, ions, or a combination of these is called a chemical bond. These are different types of bonds like a covalent bond, ionic bond, hydrogen bond, metallic bond, etc.

In this article, let us understand everything about metallic bonding, properties, and examples of a substance exhibiting metallic bonding.

What is a Metallic Bond?

Among \(118\) elements present in the periodic table, more than \(80\) elements are metals. Metals are hard solid, and they are made up of atoms. The atoms in a metal are very closely packed together. 

In simple words, the metallic bond is defined as the force that holds the atoms closely together in a metal. Metals are substances consisting of positively charged ions fixed in a crystal lattice with negatively charged electrons movingly through the crystal. 

Learn About Ionic Bond Here

Therefore, electrons act as the cohesive force which holds the metal atoms together and forms a metallic bond. The bond produced due to the combination of the electrostatic force of attraction between the electrons and the positive nuclei of metal atoms is called a metallic bond.

Different Types of Chemical Bond

A chemical bond is some sort of interatomic attraction that holds the two atoms together. Atoms combine to acquire stability and a noble gas configuration, i.e., stable configuration. Apart from the metallic bond, there are other types of bonding in different compounds. They are:

1. Ionic bond: The electrostatic force of attraction which holds together ions of combining atoms formed by the complete transfer of one or more electrons from the electropositive to electronegative atom is called an ionic bond.
   Example: Sodium chloride, Magnesium oxide, calcium chloride, etc., show this type of bonding.

2. Covalent bond:  The attractive force which comes into existence due to the mutual sharing of electrons between two atoms of similar electronegativity is having a small difference in electronegativities is called a covalent bond.
   Example: Oxygen molecule, nitrogen molecule, carbon compounds, etc., exhibit covalent bond.

3. Coordinate bond: It is a covalent bond in which both the electrons of the shared pair come from one of the two combining atoms.
   Example: Ozone, sulfur dioxide, etc., show coordinate bond.

4. Hydrogen bonding: The weak attractive force which binds the partially positively charged hydrogen atom of one molecule, with the partially negatively charged atom of some other molecules of similar or different types, or with some other negative centers of the same molecule is referred to as hydrogen bond or hydrogen bonding.
   Example: Hydrogen fluoride, water, etc., exhibit hydrogen bonding.

What is the Structure of a Metal Atom in a Metal?

The classical electrons theory, or electron sea theory or electron sea model, was proposed by Drupe and later on developed by Lorentz. According to this, in metal, the metal atom is made up of two parts. They are,

1. Electrons present in the valence shell are known as valence electrons which can be easily removed from the metal atom.
2. The rest of the atom is positively charged and is called a kernel. A kernel is the combination of a nucleus and all the shell electrons except the valence shell electrons.

How is Metallic Bond Formed? 

A metal is regarded as the sea of valence electrons in which positively charged kernels are supposed to be dipped with the direct linkage between kernels and valence electrons. Each kernel is surrounded by the number of valence electrons and vice versa. The valence electrons being very light, can move in the electron sea from one position to the other. The kernels being heavy, have comparatively negligible movement. The force of attraction between the positively charged kernels and the valence electron gives rise to the formation of metallic bonds.

Example: Sodium is a metal with the atomic number \(11\). Its electronic configuration is \({\text{Na,}}\,\left({11} \right) – 2,\,8,\,1\) or \({\text{1}}{{\text{s}}^{\text{2}}}{\text{,}}\,{\text{2}}{{\text{s}}^{\text{2}}}{\text{,}}\,{\text{2}}{{\text{p}}^{\text{6}}}{\text{,}}\,{\text{3}}{{\text{s}}^{\text{1}}}\). Electronic configuration implies there is one in the valence shell. Sodium forms a cation, i.e., sodium ion \(\left({{\text{N}}{{\text{a}}^ + }} \right)\) by the removal of one valence electron. These delocalized electrons result in the formation metallic bond between valence electrons and a positive metallic center (kernel).

Properties of Metallic Bonded Compounds

All the metals like gold, silver, iron, sodium, aluminium delocalised electrons are bonded by metallic bonds. Some of the properties of metallic bonded compounds are:

1. Meals are malleable (i.e., drawn into thin sheets) and ductile (i.e., drawn into thin wires) due to the valence electrons being very light can move in the electron sea from one position to the other in metal.
2. Metals have electrons, which can transfer energy rapidly. Therefore metals are good conductors of heat and electricity.

3. Metals are lustrous due to the absorption of radiation by the valence electrons of the metal, and they also emit light as a reflection of the original light.
4. In metals, except in mercury, intermolecular force and intramolecular forces are the same. Therefore, metals are solids at room temperature.
5. When light or heat energy is more than the attractive forces, strikes on the metal surface, electrons are emitted from the metal surface. This phenomenon is called the photoelectric effect.
6. Bonding in the metals, i.e., the metallic bond is non-directional and weaker than a covalent bond.
7. Due to the strong intermolecular force of attraction, i.e., electrostatic force of attraction between the metal ion and electrons, metals have a high melting point and boiling point.
8. Metals possess high tensile strength, that is they can stretch without breaking. It is due to the presence of strong electrostatic attraction between the positively charged kernel and the mobile electrons present around them.

What are the Factors Affecting Metallic Bond?

The metal strength varies from metal to metal. Alkaline metals are soft that they can be cut with a knife. The metals like tungsten, iron, cobalt, etc., are quite hard. The hardness of metal depends upon the strength of the metallic bonds. As bond strength increases, the hardness of the metal also increases.

According to the electron sea model, the strength of the metallic bond depends upon the following two factors.

1. The number of delocalised valence electron: The strength of the metallic bond increases with an increase in the number of delocalized valence electrons.
2. Size of the kernel: The strength of the metallic bond decreases with an increase in the size of the kernel.

Alkali metals possess only one valence electron, and their kernels are quite large. So, alkali metals have a weak metallic bond. Hence, alkali metals like sodium can be cut with a knife.

Summary

In this article, we learned that the force that holds the atoms closely together in metal is referred to as the metallic bond. Metals such as silver, iron, gold, aluminium are bonded by metallic bonds via delocalised electrons. Furthermore, we also learned that these bonds are non-directional, formed between the delocalised electrons and metal ions. Metalloid and alloys are also presented as metallic bonds. There are various factors affecting the strength of metallic bonds. The strength of the metal differs from metal to metal. We all know that alkaline metals are soft in nature whereas, metals like cobalt, iron, etc., are hard. The hardness of metal relies on the strength of the metallic bonds. The hardness of the metal increases as the metallic bond strength increases.

FAQs on Metallic Bonding

Q.1. Why does a metallic bond occur?
Ans: The metallic bond occurs due to the electrostatic force of attraction between delocalized electrons and kernels in the metal.

Q.2. How do metallic bond works?
Ans: In a metal, each kernel is surrounded by several valence electrons and vice versa. The valence electrons being very light, can move in the electron sea from one position to the other. The kernels being heavy, have comparatively negligible movement. The force of attraction between the positively charged kernels and the valence electron gives rise to the formation of metallic bonds.

Q.3. What are the characteristics of metallic bonding?
Ans: Metallic bonds are non-directional, formed between the delocalized electrons and metal ions. This bond is observed only in solids.

Q.4. In ionic bond and metallic bond, which is stronger?
Ans: The ionic bond is formed between cation and anion by the electrostatic force of attraction. But in metallic bonds, the electrostatic force of attraction is between the kernel and delocalized electron. Therefore, an ionic bond is stronger than a metallic bond.

Q.5. How do you identify a metallic bond?
Ans: In a metallic bond, a metal ion is surrounded by delocalised electrons. Hence, they can be identified by passing electricity.

Q.6. Why does metallic bonding decrease down the group?
Ans: As we move down the group, the size of metal increases due to an increase in the number of shells. Hence, the attraction between the Kernel and delocalized electron decreases. This results in a decrease in the metallic bond down the group.

Q7. Which elements form a metallic bond?
Ans: Metals show the metallic bond. Metalloid and alloys are also shown metallic bonds.

Know About Chemical Bonds Here

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