6.4 Metallic Bonding

Summary

The video explains metallic bonding, emphasizing how metals differ from ionic and covalent bonds. Unlike those, metals have free-moving electrons, forming a 'sea of electrons' that allows for efficient conductivity of electricity and heat. Metals can absorb a wide range of light frequencies due to many free electrons, making them shiny. Their malleability and ductility are attributed to their lattice structure, allowing atoms to slide past each other easily. The bond strength in metals varies and is measured by enthalpy of vaporization, which reflects the energy needed for a metal to change from liquid to gas.

Takeaways

• 🔗 Metallic bonding is neither ionic nor covalent, and metals have unique properties different from these types of bonds.
• ⚡ Metals are excellent conductors of electricity because their electrons can move freely across large sheets of metal.
• 🔬 In metallic bonds, electrons are delocalized, forming a 'sea of electrons' that can flow freely, contributing to their conductive properties.
• 📊 Alkali metals, alkali earth metals, and D-block elements have free orbitals that allow their electrons to disassociate and move freely.
• 💡 The lattice of metals, like ionic lattices, remains intact while the free electrons conduct electricity and heat.
• 🔥 Metals can transfer heat efficiently because free electrons quickly transfer momentum across the material.
• ✨ Metals are shiny and reflective because their free electrons can absorb and release a wide range of light frequencies.
• 🔧 Metals are malleable and ductile because their atomic lattice allows layers of atoms to slide past each other without breaking the structure.
• 📏 Ionic compounds lack malleability and ductility because of strong ionic repulsion, which can cause them to shear when stressed.
• 🌡️ The strength of metallic bonds varies between metals and can be measured using enthalpy of vaporization, indicating how much energy is needed for phase change from liquid to gas.

Q & A

What is metallic bonding?

Metallic bonding is a type of chemical bonding that is neither ionic nor covalent. It involves a 'sea' of delocalized electrons that are free to move across a metal lattice, allowing for properties such as electrical conductivity and malleability.

Why are metals good conductors of electricity?

Metals are good conductors of electricity because the electrons in a metallic bond are delocalized and can move freely across the metal lattice, facilitating the flow of electric current.

How do the properties of metallic bonding differ from ionic and covalent bonding?

In ionic bonding, electrons are bound to one atom, typically an anion, while in covalent bonding, electron pairs are shared between atoms but still localized. In contrast, metallic bonding allows electrons to be delocalized and move freely across the entire metal.

Which elements on the periodic table are known for their metallic bonding?

Alkali metals and alkaline earth metals, which fill the s orbital and have the p orbital completely free, are known for their metallic bonding. Additionally, most d-block elements have both their p and d orbitals free, contributing to metallic bonding.

What is the significance of the sea of electrons in metallic bonding?

The sea of electrons in metallic bonding refers to the delocalized electrons that surround the positively charged metal ions. This sea of electrons allows for the metal's high electrical conductivity, thermal conductivity, and malleability.

Why are metals shiny and reflective?

Metals are shiny and reflective because the free electrons can absorb a wide range of light frequencies, then quickly return to their ground state, releasing the absorbed energy as photons of light.

What is the role of malleability and ductility in the shaping of metals?

Malleability allows metals to be bent into thin sheets, while ductility allows them to be drawn into thin wires. These properties arise from the ability of metal atoms to slide past each other due to the lack of repulsion between them, unlike in ionic compounds.

How does the strength of metallic bonds vary between different metals?

The strength of metallic bonds varies due to factors such as atomic size and nuclear charge. These factors affect the bond strength, which can be measured by the enthalpy of vaporization.

What is the enthalpy of vaporization, and how does it relate to metallic bond strength?

The enthalpy of vaporization is the amount of energy required for a metal to transition from a liquid to a gaseous phase. It is related to metallic bond strength because this transition involves separating the metal atoms from the sea of electrons.

How does the structure of a metal lattice differ from that of an ionic compound?

A metal lattice is less robust than an ionic compound due to the absence of repulsion between metal atoms. This allows metal atoms to slide past each other easily, which is not possible in ionic compounds where such repulsion would cause layers to shear and break bonds.

What happens to the electrons in a metal when it is heated?

When a metal is heated, the electrons can quickly transfer the thermal energy (momentum) across the metal lattice, distributing the heat evenly and affecting the internal structure of the metal.