Why Do Metals Conduct Electricity? An In-Depth Explanation

30 Dec 2023 3152 Views Share

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Metals are conductors of electricity - it is something everyone is taught at a young age, for safety reasons likely. But being a science student means that you are supposed to understand the logic behind it rather than plainly mugging up facts. This is a concept students usually learn in middle school, but it is seen that they are often unclear on subject and this leads to lot of confusion in further studies. Although it seems like a basic concept, you'd be surprised to see that not everyone understands it well. So, let's dive in to find out what are the scientific properties of metals that make them conduct electricity so well. To understand this, we first need to start with learning about the different kinds of bonding.

Types of Bonds

You must have heard that the electrical conductivity of metals has something to do with â€˜metallic bondingâ€. However, to understand what metallic bonding is, we need to understand all the three broad kinds of bonds, which are as follows:

Covalent Bonds: Covalent bonds are formed by the sharing of electrons between two atoms. Two examples of common compounds that form a covalent bond are water (H2O) and carbon dioxide (CO2).
Ionic Bonds: Ionic bonds form by the complete transfer of valence electrons between a metal and a non-metal. In this process, the metal loses electrons to become positively charged cation and the non-metal accepts these electrons to become a negatively charged anion. The resulting compound, therefore, has two oppositely charged ions which attract each other. The most common example of an ionic bond is salt (NaCl) formed by Sodium and Chloride.
Metallic Bonding: Metallic bonding occurs as a result of the electrostatic static force that exists between conduction electrons and positively charged metal ions. It is the sharing of free electrons among a network of positively charged ions.

Let us understand the concept of metallic bonding in detail.

Understanding Metallic Bonding

What is difference in metallic bonding? Unlike both the other kinds of bonding, here the electrons are delocalized i.e., they are spread over more than one atom. Commonly used terms are â€˜sea of electrons' or â€˜cloud of electrons.' All of the metal atoms share their outer electrons unlike in other elements where atoms orbit a specific atom. The electrons roam all over, being shared among all the atoms.

Metal atoms form a repeating pattern and the space between them are filled with electrons that move freely. Just like in ionic bonding, the metal ions gives up electrons to the other atom, in metallic bonding, the metal ions give up the same elections to a sea of electrons. The metallic bonding holds together as every atom in it is positively charged and the negatively charged sea acts as a glue that binds all of these atoms together.

This unique type of bonding is of significance as it the reason behind all of the interesting properties of metals such as:

Shininess
Strength
Thermal conductivity
Malleability
Ductility
High melting point
Electrical conductivity

If we go into more details, we'll discover that there are many quantum-mechanics phenomenons at play. But there are simpler concepts that will give you a little more clarity on the topic without confusing you. The band gap is one of them. It explains why metals are good conductors of electricity. So let's take a look at what band gap is and how it is relevant here.

What Is Band Gap?

An electron has various possible energy states. For every electron, there are specific energy levels it can exist in. As they are energized, they hop between these stages accordingly. If enough energy is present, it is even possible for these electrons to even leave the atoms completely.

As a piece of metal contains a large number of atoms and electrons, they merge into a band of continually allowed states. This is called a valence band. Another relevant concept here is that of a conduction band, which is the band of electron orbitals that electrons can jump up into from the valence band when excited. When the electrons are in these orbitals, they have enough energy to move freely in the material.

The band gap is the distance between the valence band and the conduction band. This difference in size creates all the difference between conductors, semi-conductors, and non-conductors of electricity.

Metals have no band gap, meaning that their conduction band and valence band overlaps which leaves them in no bound to any particular atom. So, if they have enough energy to leave, they just leave.

Metals have no band gap
Semi-conductors have a small band gap
Insulators have a large band gap

This shows how metals are able to conduct electricity as they have no band gaps.

How Do Metals Conduct Electricity?

Now that you are familiar with the concepts of metallic bonding and band-gap, you are closer to understanding why do metals conduct electricity. Metals transfer electricity because of the free flow of electrically charged particles or electrons. The atoms of metals consist of valence electrons that are present in the outer shell, which move freely. These valence electrons transmit electricity and heat.

When you apply electricity to the metal, the valence electrons gain energy. It is this energy that is required by the electron to move off from its regular orbit. These electrons travel through the web-like structure of the metal. These electrons move like billiard balls under the electric field, knocking against each other, thereby passing the charge as they move. Metals can conduct the maximum amount of electricity when there is no resistance. This is why pure metals are the best conductors of electricity.

Now that we are on the topic of conductivity of different metals, not all metals conduct electricity equally. Different metals have different levels of conductivity. Conductivity essentially is the ability to conduct energy in material via electrons. The more free the electrons are, the better the chances for the transmission are. Therefore, the structure and valence of a given metal determines its conductivity. Here's a list of metals in descending order of conductivity:

Silver
Copper
Gold
Aluminum
Zinc
Nickel
Brass
Bronze
Iron
Platinum
Carbon steel
Lead
Stainless steel

To understand how and why metals conduct electricity, you need to first understand the three kinds of chemical bonding. Metallic bonding is one of three forms of bonding and it explains how if is unique as unlike other metals have a sea or web of electrons that are shared between atoms and are free to move when energized. The electrons act as a band in an energy state forming a valence band. This valence band can jump to the state of a conductive band when excited enough. The difference between the valence band and conductive band is known as the band gap, which is different in every element and this determines its conductivity. Metals are good conductors of electricity as they have no band gap. When you apply electricity to metals, the valence electrons gain energy and move freely, because of the structure and bonding of metals, which is what makes them conduct heat.

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