Question

Which of the following compounds is metallic and ferromagnetic [2016] (a) \(\mathrm{CrO}_{2}\) (b) \(\mathrm{VO}_{2}\) (c) \(\mathrm{MnO}_{2}\) (d) \(\mathrm{TiO}_{2}\)

Short answer

The compound \\text{CrO}_{2} is both metallic and ferromagnetic.

Step-by-step solution

Identify Properties of Compounds

Firstly, we need to recognize the properties under consideration: metallic nature and ferromagnetism. A substance is metallic if it has free electrons that allow it to conduct electricity. Ferromagnetism is a type of magnetism that occurs in materials, including iron and cobalt, where the magnetic moments of the atoms align parallel to each other.

Evaluate Compound \\text{TiO}_{2}

Titanium dioxide (\(\mathrm{TiO}_{2}\)) is known for being a very stable compound used mostly as a pigment. It is not known to have metallic properties or ferromagnetism. Thus, \(\mathrm{TiO}_{2}\) is neither metallic nor ferromagnetic.

Evaluate Compound \\text{MnO}_{2}

Manganese dioxide (\(\mathrm{MnO}_{2}\)) is commonly identified as a non-metallic oxide used in batteries. It is antiferromagnetic, meaning it does not exhibit ferromagnetism as its magnetic moments are opposite rather than parallel. Hence, \(\mathrm{MnO}_{2}\) is not metallic or ferromagnetic.

Evaluate Compound \\text{VO}_{2}

Vanadium(IV) oxide (\(\mathrm{VO}_{2}\)) can undergo a phase transition that allows it to be metallic, but it is not ferromagnetic. Therefore, \(\mathrm{VO}_{2}\) only occasionally exhibits metallic features and is not known to be ferromagnetic.

Evaluate Compound \\text{CrO}_{2}

Chromium(IV) dioxide (\(\mathrm{CrO}_{2}\)) is well-known for being a ferromagnetic compound, often used in magnetic recording. It possesses metallic conductivity because it has free electrons facilitating the electron motion. Therefore, \(\mathrm{CrO}_{2}\) fits both the criteria of being metallic and ferromagnetic.

Key concepts

Metallic Properties

Metallic properties are fascinating characteristics that define metals and some metal oxides. These properties include the ability to conduct electricity and heat, which is primarily due to free electrons. In a metallic structure, electrons can move freely, allowing currents to pass through with ease. This contributes to the shiny appearance and malleability seen in metals like copper and aluminum.

Some key metallic properties include:

• Conductivity: Metals can transfer electrical charges due to their free-moving electrons.
• Luster: Metals often have a shiny surface because they reflect light.
• Malleability: Metals can be hammered or rolled into sheets without breaking.

Understanding these properties helps in identifying materials like \(\mathrm{CrO}_{2}\), which shows both metallic and magnetic characteristics.

Chromium Dioxide

Chromium dioxide (\(\mathrm{CrO}_{2}\)) is a compound that stands out due to its unique properties, especially among its oxides. Not only is it metallic, but it is also ferromagnetic, a trait not commonly found together in metal oxides.

In the context of technological applications, \(\mathrm{CrO}_{2}\) is most recognized for its role in magnetic recording media. This is due to its ability to maintain a permanent magnetic moment, aligning easily with external magnetic fields.

• Usage: Extensively used in magnetic tapes and storage devices.
• Structure: Chromium ions in \(\mathrm{CrO}_{2}\) help align the magnetic domains, contributing to its ferromagnetic nature.

This combination of properties makes \(\mathrm{CrO}_{2}\) a significant material in both the study and application of magnetic materials.

Electrical Conductivity

Electrical conductivity refers to the capacity of a material to allow the flow of an electric current. It’s a critical property when determining whether a substance can be classified as metallic. It depends largely on the availability of free charges, typically electrons, that can move through a material.

In the case of metals and some metal oxides, free electrons provide a means by which electricity can be conducted efficiently through the lattice structure. Chromium dioxide is an example of a compound with high electrical conductivity due to its free electron availability.

• Conduction Mechanism: In conductive materials, electrons move in response to an electric field.
• Applications: Materials with high electrical conductivity are crucial for circuits and electronic devices.

Understanding conductivity is vital in applications ranging from electronic components to power transmission.

Magnetic Materials

Magnetic materials exhibit the extraordinary ability to attract iron and influence other materials through magnetic fields. The most striking type of magnetic behavior is ferromagnetism. Ferromagnetic materials, like \(\mathrm{CrO}_{2}\) and iron, show strong attraction and can retain magnetization even after an external field is removed.

These materials have domains—regions where magnetic moments are aligned in a consistent direction. Under an external magnetic field, these domains align more perfectly, amplifying the material's overall magnetism.

• Ferromagnetism: Characterized by strong, permanent magnetic properties.
• Paramagnetism: Materials are weakly attracted by a magnetic field and do not retain magnetism.
• Diamagnetism: Materials are weakly repelled by a magnetic field.

By understanding the properties and behavior of magnetic materials, we can create advanced technological systems, improve data storage solutions, and innovate in medical imaging techniques.