Metal

Jai Ganesh · Today 18:17:15

Metal

Gist

A metal is a material that is typically hard, strong, shiny, and an excellent conductor of heat and electricity. It can be shaped by hammering (malleability) or drawn into wires (ductility). The term can refer to a chemical element (like iron, copper, or gold), a mixture of elements (like steel), or the music genre, heavy metal.

A metal is a material that is typically hard, shiny, and an excellent conductor of heat and electricity. Common characteristics include being malleable (can be hammered into sheets), ductile (can be drawn into wires), and having a high melting point. Metals are elements found on the periodic table that readily lose electrons to form positive ions. Examples include iron, copper, aluminum, and gold.

Summary

A metal is any of a class of substances characterized by high electrical and thermal conductivity as well as by malleability, ductility, and high reflectivity of light.

Approximately three-quarters of all known chemical elements are metals. The most abundant varieties in the Earth’s crust are aluminum, iron, calcium, sodium, potassium, and magnesium. The vast majority of metals are found in ores (mineral-bearing substances), but a few such as copper, gold, platinum, and silver frequently occur in the free state because they do not readily react with other elements.

Metals are usually crystalline solids. In most cases, they have a relatively simple crystal structure distinguished by a close packing of atoms and a high degree of symmetry. Typically, the atoms of metals contain less than half the full complement of electrons in their outermost shell. Because of this characteristic, metals tend not to form compounds with each other. They do, however, combine more readily with nonmetals (e.g., oxygen and sulfur), which generally have more than half the maximum number of valence electrons. Metals differ widely in their chemical reactivity. The most reactive include lithium, potassium, and radium, whereas those of low reactivity are gold, silver, palladium, and platinum.

The high electrical and thermal conductivities of the simple metals (i.e., the non-transition metals of the periodic table) are best explained by reference to the free-electron theory. According to this concept, the individual atoms in such metals have lost their valence electrons to the entire solid, and these free electrons that give rise to conductivity move as a group throughout the solid. In the case of the more complex metals (i.e., the transition elements), conductivities are better explained by the band theory, which takes into account not only the presence of free electrons but also their interaction with so-called d electrons.

The mechanical properties of metals, such as hardness, ability to resist repeated stressing (fatigue strength), ductility, and malleability, are often attributed to defects or imperfections in their crystal structure. The absence of a layer of atoms in its densely packed structure, for example, enables a metal to deform plastically, and prevents it from being brittle.

Details

A metal is a material that, when polished or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. These properties are all associated with having electrons available at the Fermi level, as opposed to nonmetallic materials which do not. Metals are typically ductile (can be drawn into a wire) and malleable (can be shaped via hammering or pressing).

A metal may be a chemical element such as iron; an alloy such as stainless steel; or a molecular compound such as polymeric sulfur nitride. The general science of metals is called metallurgy, a subtopic of materials science; aspects of the electronic and thermal properties are also within the scope of condensed matter physics and solid-state chemistry, it is a multidisciplinary topic. In colloquial use materials such as steel alloys are referred to as metals, while others such as polymers, wood or ceramics are nonmetallic materials.

A metal conducts electricity at a temperature of absolute zero, which is a consequence of delocalized states at the Fermi energy. Many elements and compounds become metallic under high pressures, for example, iodine gradually becomes a metal at a pressure of between 40 and 170 thousand times atmospheric pressure.

When discussing the periodic table and some chemical properties, the term metal is often used to denote those elements which in pure form and at standard conditions are metals in the sense of electrical conduction mentioned above. The related term metallic may also be used for types of dopant atoms or alloying elements.

The strength and resilience of some metals has led to their frequent use in, for example, high-rise building and bridge construction, as well as most vehicles, many home appliances, tools, pipes, and railroad tracks. Precious metals were historically used as coinage, but in the modern era, coinage metals have extended to at least 23 of the chemical elements. There is also extensive use of multi-element metals such as titanium nitride or degenerate semiconductors in the semiconductor industry.

The history of refined metals is thought to begin with the use of copper about 11,000 years ago. Gold, silver, iron (as meteoric iron), lead, and brass were likewise in use before the first known appearance of bronze in the fifth millennium BCE. Subsequent developments include the production of early forms of steel; the discovery of sodium—the first light metal—in 1809; the rise of modern alloy steels; and, since the end of World War II, the development of more sophisticated alloys.

Additional Information

The term “metal” applies to a large portion of the periodic table of elements. Metals are typically characterized by high electrical and thermal conductivity, luster, and, in many cases, notable malleability, ductility, and tensile strength. Most are solid at room temperature and readily form metallic bonds. They are a core pillar of most product market segments thanks to their advantageous properties and broad versatility.

What Is Metal?

Metal elements are characterized by several distinct physical and chemical properties. They are typically found toward the left side of the periodic table and are distinguished by their ability to form positive ions (cations) via the loss of electrons. These cations form metallic bonds with free electrons, allowing them to move freely among the metal atoms. This bonding structure contributes to their unique properties, such as ductility, conductivity, and strength.

What Are the Different Properties of Metal?

The common properties of metals are listed and discussed below:

1. Density

Density is a fundamental physical property, quantifying mass per unit volume. Metals, on average, exhibit higher densities than non-metals, influenced by factors like atomic structure, atomic number/mass, and crystalline/atomic packing arrangement. Variations in composition, temperature, and pressure impact metal density; pure metals often boast higher densities than alloys.

2. Electronegativity

Electronegativity is a measure of an atom's electron-attracting capability when forming molecular bonds. In metals, it underpins their chemical behaviors and interactions. Metals typically exhibit low electronegativity compared to non-metals, signifying weaker electron attractions during bond formation. Consequently, metals readily donate electrons to nearby atoms, yielding positively charged ions (cations) that can then form ionic compounds or metallic bonds.

When forming bonds, metal ions are enveloped by a sea of delocalized electrons, enabling efficient electricity and heat conduction. Metals react with non-metals, forming ionic compounds with high melting points. Some such reactions generate impermeable oxide coatings like aluminum oxide or chromium oxide, while others, like iron oxide (rust), allow further degradation. Almost all metals oxidize readily when conditions allow.

3. Luster

Luster defines how light interacts with a material's surface and how well it reflects to the observer. Metals' electron configuration and metallic bonding enable strong electromagnetic (EM) reflection. Incident light interacts with delocalized electrons in the lattice. They’re easily absorbed and re-emitted, imparting a characteristic brilliance to the macroscopic surface.

Luster varies with surface finish, purity, and crystal structure, with polished surfaces exhibiting greater reflectivity. Beyond aesthetics, luster holds practical significance because it reflects infrared and radio frequencies in addition to visible light.

4. Malleability

Malleability denotes a material's ability to endure compressive stress and deform without fracturing. This trait defines metals’ utility and adaptability. Metallic bonding and regular crystalline structure enable metal atoms to glide over one another under pressure, remaining in lattice contact by delocalized electrons circulating among metal ions.

Malleability varies based on microscopic crystal structure, temperature, and purity. Metals with the closest-packed microstructure, like gold and silver, are the most malleable. Malleability facilitates forging, stamping, and rolling, among other processes.

5. Opacity

Metals’ electronic structure makes them opaque in the visible spectrum. When light interacts with a metal surface, it encounters free electrons, which absorb and scatter photons. This scattering prevents light from passing through in a straight line, resulting in opacity. Metals absorb many wavelengths of light, including the visible spectrum, so they’re highly opaque.

Overall, electronic structure, electron mobility, and light scattering within the lattice combine to make metals opaque at all visible frequencies and more or less reflective across most spectra. This property influences laser-based machining methods, thermal control/dissipation applications, and aesthetic roles.

6. Ductility

A metal’s intrinsic ductility determines how it can be formed into useful shapes. Metallic bonding fosters high ductility, as atomic layers slide over each other under stress. Ductility varies across metals, and it is affected by purity, crystalline structure, and other factors. More densely packed crystal structures, like those in gold and silver, show higher ductility.

This is a key property for metals drawn into wires, rods, or thin sheets for electrical wiring, cables, and metal foils. Ductility also enables intricate component shaping via forging, extrusion, and rolling.

7. Hardness

Hardness gauges a material's resistance to deformation, scratching, or penetration. In metals, it has functional significance, dictating the products’ durability. Standardized tests like Rockwell, Vickers, or Brinell measure hardness.

Atomic structure and bonding have the biggest influence on metal hardness — densely packed crystal structures like face-centered cubic (FCC) or body-centered cubic (BCC) translate into harder metals. Alloying elements, grain size, and heat treatment also impact hardness. Hardness guides material selection — hard metals find use in tools and wear-resistant coatings, while softer ones are critical in resilient structural components for buildings and vehicles.

8. Conductivity

Conductivity describes a material's ability to conduct electricity or heat. Both are crucial features in many metal applications.

The free electrons in a metal’s crystal structure enable excellent electrical current flow. This property is found in wiring, circuits, and electronics. For the same reason, metals generally exhibit high thermal conductivity, facilitating heat transfer via lattice vibrations and free electron movement. Applications span from heat exchangers to cooking utensils. Conductivity hinges on factors like crystal structure and purity; dense structures like copper and silver exhibit superior conductivity. These inherent conductive qualities are important factors in material selection for electronics and thermal management items.

9. High Tensile Strength

Tensile strength describes a material's ability to resist tensile forces without permanent deformation. It's key for structural and load-bearing applications, and metals are usually far stronger in tension than are polymers or ceramics.

Metallic bonding underpins this strength — the atoms shift elastically under tension. Tensile strength varies with factors like composition, crystal structure, grain size, and processing. Metals with greater crystallinity, smaller grains, and higher purity exhibit superior tensile strength.

10. High Reflectivity

Reflectivity defines a material's ability to reflect light or other electromagnetic radiation. It is essentially the same as luster but applies to a larger frequency range, from X-ray/UV to long-wave radio. Nevertheless, the mechanisms of reflectivity are the same as those describing luster.

11. Sonorousness

Sonorousness characterizes a material's ability to produce resonant sound upon impact, a hallmark of most metals. This property stems from the fact that sound waves propagate easily through metallic crystalline structures. Sound reflection further extends the sound effects. Striking a metal object, like a bell or plate, induces highly elastic vibrations that travel through the lattice, resulting in clear, ringing tones. The macro effect is shape oscillations that induce sound waves in the surrounding air.

Practical applications abound, particularly in musical instruments where metals produce rich, resonant sounds. Additionally, sonorous metals are used in acoustic engineering, enhancing sound reflection and architectural acoustics in buildings and performance spaces.

12. High Melting and Boiling Points

Most metals exhibit very high melting and boiling points (MP and BP). The most notable exceptions are lead, tin, gallium, and mercury. Metallic bonding is responsible for these characteristics, with variations in atomic size and packing density affecting specific values.

Tungsten and molybdenum have high MPs and may be added as alloying agents to raise the MP of various materials for high-temperature machinery. Tantalum also has a high BP, benefiting vacuum systems.

13. Corrosion Resistance

Corrosion resistance describes the material’s durability amid exposure to corrosive elements like moisture, chlorides, acids, and alkalis. It safeguards structural integrity and aesthetics for all types of products.

Metals can corrode via oxidation or other chemical reactions, leading to surface defects and weakened structures. Factors like composition, treatments, and environment influence resistance.

Stainless steel, nickel, chromium, zinc, aluminum, and titanium excel because they form impermeable and self-healing oxide layers on their surfaces. Many cheaper but high-performing metals, like steel, require coatings or alloying. Steel can be coated in zinc or alloyed with chromium to resist oxidation. Gold and silver are both highly resistant to corrosion under typical conditions, with gold being virtually immune to most corrosive agents.

14. Magnetic Properties

Metals’ magnetic properties arise from their electron configuration and atomic arrangement. They are categorized into three types: ferromagnetic, paramagnetic, and diamagnetic metals. Ferromagnetic metals exhibit strong magnetic responses to external magnetic fields and will retain their magnetic alignment after being exposed to a magnetic field. Paramagnetic metals, on the other hand, are weakly attracted to magnetic fields but lose magnetization once the field is removed. Diamagnetic metals are repelled by magnetic fields and possess no net magnetization.

These three properties enable applications in magnetic storage, electromagnets, magnetic shielding, magnetic braking, and MRI machines.

15. Solid State at Room Temperature

Metals typically remain solid at room temperature due to the robust metallic bonds between atoms. The arrangement and strength of metallic bonds, influenced by factors like valence electrons and atomic size, dictate the melting point.

What Is the Use of Metal?

Metals have a plethora of applications owing to their physical, mechanical, and chemical properties. They are ideal for structural applications like construction and transportation, enduring heavy loads and harsh loading conditions. Their electrical and thermal conductivity makes metals vital in electrical wiring, electronics, and heating/cooling systems. Metals' malleability and ductility allow easy shaping and fabrication. Some offer excellent corrosion resistance, ideal for outdoor, marine, and chemically aggressive environments. High recyclability means metals can be reused, reducing the environmental impact of primary extraction and waste disposal. Some metals are visually appealing enough for jewelry and architectural finishes. Metals' high melting and boiling points ensure they retain mechanical strength, demanding high-temperature applications.

Math Is Fun Forum

#1 Today 18:17:15

Metal

Board footer