What is Metallic Bond?

Metallic Bond

You must have read about metals and other metallic objects. Even you have seen a lot of objects made up of metals. Have you ever wondered what causes different shapes and variations in metallic objects? Why can we make sheets, wire, or any other form of metal? Why do they shine when exposed to light?

What is the connection between one atom of metal and another, and what makes them connected? There are so many fascinating things about metals. But, the reason for most of these causes is metallic bonding.

This article will let you learn about metallic bonding and answer the above questions. Have a look.

 What is Metallic Bonding?

Metallic bonding is the force of attractiveness between valence electrons and metal ions. A chemical bonding arises from the attractive electrostatic force between conduction electrons and positively charged metal ions.

What is metallic bonding? It is described as sharing free electrons among a lattice of positively charged ions (or cations). A metallic bond is an impact that holds the metal ions together in the metallic object. It is a force of attraction between the metallic cations and the delocalised electrons, and this force binds the atoms firmly together in the metallic object.

A metallic bond is electrostatic and only exists in metallic objects. Metallic bonding describes many physical features of metals, such as lustre, flexibility, electrical and thermal conductivity and resistivity, opacity, and strength.

 How is a Metallic Bond Formed?

In the case of the metallic object, the integral particles are fixed metallic cations surrounded by a sea of mobile electrons. These are produced from metallic objects because such objects have low ionisation energy and can easily lose their valence electrons to leave behind positively charged ions (kernels).

These electrons can penetrate easily throughout the metallic lattice, like water in the sea. So, these are called the ‘sea of free electrons.’

Each metallic atom contributes one or more electrons towards this sea of delocalised electrons. These mobile electrons are simultaneously attracted by the positive ions and hold these positive ions together by the electrostatic force of attraction.

The attraction between the kernel and the mobile electrons that hold the kernel together and this force of attraction is known as a metallic bond. The essential particles in metallic crystals are metal atoms held together by a metallic bond.

The following metallic bonding diagram shows the metallic solid-positive ions in a sea of mobile electrons.

Metallic Bond Examples

Generally, all metals are metallic bond examples. But, here are explanations of metallic bonding in some metals, i.e., aluminium, magnesium, and sodium.

The electronic configuration of aluminium (Al) is 1s² 2s²  2p⁶ 3s² 3p¹. It has three valence electrons in total. Due to its electropositive nature and delocalised electrons, it can lose these three valence electrons and become Al+3 metallic ions. With such a positive charge, individual Al ions can strongly repel each other. But the sea or cloud of electrons held them together. Due to the greater magnitude of charge and electron density, the melting point of aluminium becomes higher than that of magnesium and sodium.

In the case of magnesium (Mg), electronic configuration 1s² 2s² 2p⁶ 3s², and sodium (Na), electronic configuration 1s² 2s² 2p⁶ 3s¹, the number of valence electrons is 2 and 1, respectively. As a result, their electron density and magnitude of the charge are lower than aluminium. Hence, their melting points are also lower than aluminium.

Therefore, the metallic bonding of aluminium would be stronger than magnesium and sodium. In fact, because of the low number of free electrons, sodium is soft and has a lower melting point than the other two.

 Metallic Bonding Formation Factors

The factors favouring the formation of metallic bonds are:

• The ionisation energy of the metal should be low so that the valence electrons are loosely held by the nucleus and thus become mobile.
• The metals should have high electropositivity, so they do not accept electrons and form anions.
• The vacant orbital should be more than the number of valence electrons so that the mobile electrons can easily move in the vacant orbitals.

 Characteristic Properties of Metallic Bonds

Some important characteristic properties of solids containing metallic bonds are:

1. Electrical conductors:

Metallic bonding crystals are generally good conductors of electricity. It is because of a sea of free electrons in their structure. Their metallic crystal has mobile or delocalised electrons. When the one end of this crystal comes in contact with an electric field, the mobile electron present there moves towards the positive end of the crystal. When it moves, another electron grasps its position and faces the same situation. In this way, the movement of electrons occurs, leading to the flow of electricity in the crystal. Therefore, solids having metallic bonds are good conductors of electricity.

2. Thermal conductors:

Like electrical conductivity, metallic crystals are good conductors of heat. It is because when heat is given to one part of the metallic lattice, the delocalised electrons at that end start to absorb the heat energy. After that, these electrons start moving toward the lattice’s cool end. This way, the heat is transferred from one end of the lattice to the other. Hence, it makes them good thermal conductors. The thermal conductivity of metallic objects decreases with an increase in temperature.

3. Lustrous:

They possess lustre and colour in some cases. It is also explained based on mobile electrons present in the metallic lattice. Light collides with the free electrons when it falls on the lattice surface. As a result, these electrons get excited and revert from their original positions. During this movement, they release some energy in the form of light.

4. Opaque:

They are opaque. It is because when the light falls on metallic objects, the light is absorbed completely by the electronic transition of the sea of electrons. Hence, no light is permitted to pass through them.

5. Malleable and Ductile:

They are highly malleable (converted into thin sheets) and ductile (converted into thin wires). When a metallic crystal is beaten, the top layer of positive metal ions move. After that, another layer takes its place. Because of their mobile nature in metallic objects, electrons also move with the positive metallic layer.

Therefore, the position of the positive ions is altered without destroying the structure of the substance, and the freely moving electrons provide a uniform distribution of charges. For this reason, they are easily deformable.

6. High boiling and melting point:

As the position ions are closely packed in the substances containing metallic bonds, most possess high boiling and melting points and have high densities.

7. Alloy formation:

Metallic mixtures are called alloys. Metallic objects can form alloys easily. In these alloys, the spherical ions of different atoms share the same sea of electrons.

Conclusion

Metallic bonding is a chemical bonding that occurs connecting atoms of metallic objects. The chief force holds together the atoms of a metallic crystal. Metallic bonds result from sharing a variable number of electrons with a variable number of atoms. It gives metals their distinctive properties. 

Frequently Asked Questions

Q1. What are the applications of the metallic bond?

Answer: Metallic bonds hold metal together, but they also generate that sea of electrons that allows electrons to flow. Without this sea of electrons devised by metallic bonds, we couldn’t have all the pleasurable things electricity brings.

Q2. What are the differences between metallic bonds and ionic bonds?

Answer: The important differences between metallic bonds and ionic bonds are:

Metallic Bond	Ionic Bond
This bond is formed by the simultaneous attractive interaction between the kernels (positively charged metal atoms) and mobile electrons in a metal crystal.	This bond is devised by the transfer of electrons between two dissimilar atoms.
Metals are malleable.	Ionic compounds are brittle.
It is a weak bond.	It is a strong bond due to the strong electrostatic force of attraction.
Metals are good conductors in the solid-state.	Ionic compounds are bad conductors in the solid-state.

Q3. What are the differences between metallic bonds and covalent bonds?

Answer: Differences between metallic bonds and covalent bonds are:

Metallic Bond	Covalent Bond
This bond is formed by the simultaneous attractive interaction between the kernels and mobile electrons in a metal crystal.	This bond is formed by sharing electrons between two similar or dissimilar atoms.
It is a weak bond because many nuclei simultaneously attract mobile electrons.	It is a strong bond because nuclei strongly attract the bonded electron pair (or pairs).
Metals are usually solid.	Covalent compounds are usually liquids and gases.
Metals are good conductors of electricity.	Generally, covalent solids are bad conductors of electricity (graphite is an exception).
This bond is non-directional.	This bond is directional.

Q4. How is the metallic bond responsible for the higher melting and boiling point of transition metals than alkali metals?

Answer: The strength of the metallic bond depends on the number of valence electrons and the charge on the nucleus. As the number of valence electrons and the charge increases, the strength of the metallic bond increases. Due to this reality, alkali metals are soft and have low melting and boiling points, while transition metals are hard and have high melting and boiling points.