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Mastering Metallic Bonding: The Key to Understanding Metals
Dive into the world of metallic bonding and discover how it shapes the properties of everyday materials. Learn about electron seas, conductivity, and the unique characteristics that make metals indispensable in modern life.

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Now Playing:Metallic bonding – Example 0a
Intros
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  1. What is metallic bonding?
  2. Features of metallic bonding.
  3. Explaining metal properties.
Introduction to bonding
Jump to:NotesConceptFAQsPrerequisites
Notes

In this lesson, we will learn:

  • To describe the features of metallic bonding and the structure of pure metals.
  • How to explain the properties of metals using metallic bonding theory.
  • How to explain the trends in properties of metals using metallic bonding theory.

Notes:

  • We saw earlier that ionic and covalent bonding are bonding types that hold compounds and small molecules together, but in elemental metal samples (pure metals, not metal compounds) there is a third type of bonding called metallic bonding.

  • In elemental metals (that means pure iron metal, not iron compounds), metallic bonding creates a structure with the following features:
    • There is a lattice of positively charged metal ions.
    • Between these positive ions, there is a sea of negative delocalised electrons. These are the electrons that the metal atoms (that are now ions!) had lost, so they could gain a full outer shell.
    The attractive force that keeps the structure together is the positive/negative electrostatic attraction between these two features.
    See the diagram below but remember that the electrons are freely moving, thats why they look a bit disorganised.

    Metallic bonding

  • Metallic bonding, occurs in samples of metal-only atoms, including pure metallic samples, and explains the properties of pure metals that we observe.
    • Metallic bonding occurs in PURE METAL SAMPLES. It occurs in alloys too, which are mixtures of different metals we will look at next lesson.
    • Metallic bonding does NOT occur in metal compounds with non-metal atoms. That is ionic bonding which we learned in C11.4.2: Ionic and covalent bonding

  • As with any bonding theory, we use our ideas of metallic bonding to help explain the properties that we see when we study metals. Metallic bonding explains the properties of metals in the following ways:
    • There is a strong electrostatic attractive force between the metal ions and the delocalised electrons. It takes a lot of energy to overcome this force and pull the positive ions apart from the delocalised electrons. This is why most metals have a high melting point.
    • The sea of delocalised electrons is fluid. This means the metal ions can move amongst and around each other because they arent rigidly stuck in one place in the lattice. This is why many pure metals are both malleable and ductile:
      • A material that is malleable can be bent and re-shaped when it is heated up. This is how blacksmithing works (how swords and iron tools are made), as hot metal is hammered into different shapes before it hardens as it cools.
      • A material that is ductile can be bent and drawn into thin wires. Copper is very ductile and most electrical wires are made from it.
    • The fluid sea of negatively charged delocalised electrons easily carry electric charge and heat energy throughout the lattice.
      • This explains why metals are good conductors of both electricity and heat.

  • There are trends in properties of metals, like their melting point. The trends are caused by different metallic bonding strength which is caused by two main factors:
    • The charge of the metal ion in the lattice. For example, compare group 1 metals that have a 1+ ion charge and group 2 metals with ions of 2+ charge. If you compare a group 1 and group 2 metal in a period like Na and Mg, the group 2 metal will have a higher melting point because of the greater charge difference.
      In short, 2+ attracting 2- is a stronger force than 1+ attracting 1-.
    • The ionic radius of the ion. In Periodic trends: Atomic radius, we saw that the ionic radius gets larger going down a group in the periodic table.
      This means the nucleus (where the positive charge is) is further away from the delocalised electrons it is attracted to, so a larger ionic radius makes a weaker metallic bond. You can see this in the melting and boiling points of metal elements decreasing down the group column.

  • Metallic structure and bonding is not only seen in pure metals, but also in mixtures of different metals combined ‐ these are called alloys. Alloys are made to obtain unique or more precise properties of two or more metal elements. We will look at alloys in our next lesson, Alloys.
Concept

Introduction to Metallic Bonding

Metallic bonding is a fundamental concept in chemistry that explains the unique properties of metals. Our introduction video provides a comprehensive overview of this essential chemical bonding type, making it easier for students to grasp the concept. Metallic bonding occurs when metal atoms share their valence electrons, creating a "sea" of delocalized electrons. This electron sea is responsible for the characteristic properties of metals, such as high electrical conductivity and thermal conductivity, malleability, and ductility. Understanding metallic bonding is crucial for comprehending the behavior of everyday materials, from the aluminum in soda cans to the copper in electrical wires. The video explores how this bonding type differs from covalent and ionic bonds, and its significance in various applications. By mastering the concept of metallic bonding, students gain valuable insights into the structure and properties of materials that shape our modern world.

FAQs

Here are some frequently asked questions about metallic bonding:

  1. What is a metallic bond in simple terms?

    A metallic bond is a type of chemical bond that occurs between metal atoms. In this bond, the outer electrons of metal atoms are shared in a "sea" of delocalized electrons, while the positively charged metal ions form a lattice structure. This arrangement allows for the unique properties of metals, such as high electrical conductivity and malleability.

  2. What is the difference between metallic and covalent bonding?

    Metallic bonding involves the sharing of electrons among many metal atoms, creating a sea of delocalized electrons. Covalent bonding, on the other hand, involves the sharing of electrons between specific atoms to form discrete molecules. Metallic bonds result in properties like conductivity and malleability, while covalent bonds often form gases, liquids, or network solids with different properties.

  3. How do metallic bonds stay together?

    Metallic bonds are held together by the electrostatic attraction between the positively charged metal ions and the negatively charged sea of delocalized electrons. This strong attraction keeps the metal atoms in a cohesive structure, allowing for the characteristic properties of metals.

  4. What are some examples of metallic bonds?

    Examples of metallic bonds can be found in pure metals like copper, silver, gold, iron, and aluminum. Alloys, such as steel (iron and carbon) and brass (copper and zinc), also exhibit metallic bonding. These materials showcase properties like electrical conductivity, thermal conductivity, and malleability due to their metallic bond structure.

  5. Do metallic bonds have high melting points?

    Generally, yes. Metallic bonds often result in high melting points due to the strong attraction between the positive metal ions and the sea of electrons. However, the melting point can vary depending on the specific metal. Some metals, like tungsten, have extremely high melting points (3,422°C), while others, like mercury, have low melting points (-38.83°C). The strength of the metallic bond, influenced by factors such as the number of valence electrons and atomic size, determines the melting point.

Prerequisites

To fully grasp the concept of metallic bonding, it's crucial to have a solid foundation in several key areas of chemistry. Understanding these prerequisite topics will significantly enhance your ability to comprehend the unique properties and behaviors of metals in chemical interactions.

One of the most important concepts to master is electrical conductivity. Metals are known for their high electrical conductivity, which is a direct result of their bonding structure. This property is fundamental to metallic bonding, as it explains how electrons can move freely within the metal lattice, contributing to the characteristic "sea of electrons" model.

Another critical prerequisite is understanding ionic and covalent bonding. While metallic bonding is distinct from these types, comparing and contrasting it with ionic and covalent bonding helps in appreciating the unique nature of metallic bonds. Unlike covalent bonding, where electrons are shared between specific atoms, metallic bonding involves a more delocalized sharing of electrons across the entire structure.

Familiarity with the history and development of the periodic table is also invaluable. The periodic table trends play a crucial role in predicting and explaining metallic properties. Understanding how elements are arranged and how their properties change across periods and groups provides insight into why certain elements form metallic bonds while others don't.

The concept of electrical conductivity in metals is directly linked to their bonding structure. In metallic bonding, the outer electrons of metal atoms are loosely held and can move freely throughout the metal's structure. This "sea of electrons" is what gives metals their high electrical conductivity. By understanding this prerequisite, students can better grasp why metals are excellent conductors and how this property relates to their bonding.

Knowledge of ionic and covalent bonding serves as a comparative basis for understanding metallic bonding. While ionic bonds involve the transfer of electrons and covalent bonds involve sharing electrons between specific atoms, metallic bonding is characterized by a sharing of electrons across the entire metal structure. This understanding helps in differentiating the unique properties of metals from those of ionic and covalent compounds.

Lastly, the periodic table trends are essential in predicting metallic behavior. Elements on the left side of the periodic table, particularly in groups 1-3, are more likely to form metallic bonds. Understanding these trends helps in predicting which elements will exhibit metallic properties and how these properties might vary across the periodic table.

By mastering these prerequisite topics, students will be well-equipped to delve into the complexities of metallic bonding, understanding not just the what, but also the why behind the unique properties and behaviors of metals in chemical interactions.