Tin Metal: Definition, Properties and Applications

Group 14 of the periodic table contains tin metal, commonly known as Stannum in Latin, which has an atomic number of 50. Tin has two main oxidation states: +2 and the marginally more stable +4, and it exhibits chemical similarities to both of its neighbors in group 14—germanium and lead. Tin is a moderately soft, pliable, silver-white metal. The main source of tin that is mined for commercial purposes is cassiterite (tin dioxide), a mineral that is commonly found in nature. It has a density of roughly 7.3 g/cm³ and a relatively low melting point for a metal. Due to its malleability, tin may be pulled into wires and rolled into thin sheets.

Tin is rarely used as a pure metal due to its extreme softness; instead, it is mixed with other metals to create alloys that have many of tin’s advantageous qualities. These consist of a high resistance to corrosion and a low level of toxicity. Additionally, tin is ductile—it can be stretched without tearing—and malleable—it is simple to press into shape and break without breaking.

What is Tin?

Tin is a chemical element with the symbol Sn (from the Latin word “stannum”) and atomic number 50. It is a silvery-white, soft, and malleable metal that is known for its resistance to corrosion and its ability to form various useful alloys.

• Since ancient times, tin has been understood and utilized. For instance, the alloy of copper and tin gave rise to the name of the Bronze Age. Tin’s application in alloying was vital to the development of many early technologies and human history.
• Pure tin is composed only of tin atoms since it is an elemental metal. In the periodic table, it is a member of Group 14. It is designated as element number 50 and has fifty protons. Although a 69-neutron configuration is the usual state, tin isotopes can have anywhere from 62 to 76 neutrons due to their remarkable stability.
• The main source of tin is the mineral cassiterite (SnO₂), which is mined in a number of nations, including Bolivia, China, Indonesia, Peru, and others. It is found in alluvial deposits. Roasting the cassiterite ore to turn it into tin oxide and then reducing it with charcoal to extract the metal are the steps in the extraction process.
• Tin is relatively soft and can be cut with a knife. It has a low melting point of 232°C (449.6°F), which makes it easy to work with in a variety of applications. It is also highly ductile and can be drawn into wires.
• Although tin is resistant to corrosion from water, acids, and alkalis can still damage it. Its resistance to airborne oxidation aids in the long-term preservation of the metal and its alloys.
• When used as an alloying agent to mix with other metals, tin is especially useful. Tin can be found in a variety of alloys, such as pewter, babbitt metal, bronze, and solders. Many chemicals, including organotin compounds, which are utilized as catalysts and stabilizers, are made from tin compounds.
• Tin is used to cover cans; steel containers with a tin coating are frequently used to preserve food. Tin alloys are used in a variety of applications, such as dental amalgams, bell metal, pewter, dental amalgams, and solder for connecting pipes and electrical circuits. Superconducting magnets use niobium-tin alloy, whereas ceramics and gas sensors use tin oxide (which can be monitored as its electrical conductivity increases when it absorbs a gas). Aluminum foil has supplanted tin foil as a popular material for food and medication packaging.
• Overall, tin’s versatility and wide range of applications, from historical uses in bronze making to modern uses in electronics and coatings, make it an important and valuable metal.

How Is Tin Metal Made?

• Tin metal extraction and refinement entail several processes. Most commonly, open-pit or underground mines are used to produce tin ore.
• The main source of tin ore is cassiterite, which is typically mined along with gangue impurities. To concentrate the tin-bearing rocks and eliminate the gangue minerals, the mined ore is treated. Crushing and grinding are used in this process, and then gravity separation using relative buoyancy sorting procedures is carried out. As a result, the ore’s tin content rises, requiring less volume to be processed.
• In a furnace, carbon is used to heat the concentrated tin ore (typically in the form of coal or charcoal).
• As a result of the carbon preferentially oxidizing and leaving the tin as a pure metal, this process reduces the tin oxide in cassiterite to generate tin metal and carbon dioxide gas. Iron, copper, and other metal impurities will be present in the resulting unrefined “tin” metal.
• To get rid of these impurities, purify the metal in the following step. The most common method is temperature-controlled liquation, when the metal is heated to dissolve the tin content while keeping the remaining components as separable solids.
• Often, electrolytic refining is used for further purification. This method involves dissolving impure tin in an electrolyte solution and passing a direct current through it. When tin ions go to the cathode, pure tin metal is formed free of non-metallic impurities. Carefully controlling the electrode voltage and current is necessary to remove other metals. Depending on how it will be used, the resulting high-purity tin is cast into bars, sheets, or ingots.

Characteristics of Tin Metal

• Appearance: Tin is a silvery-white metal with a bright, lustrous surface when freshly cut. It can develop a dull gray patina over time due to oxidation.
• Ductility and Malleability: Tin can be rolled or hammered into thin sheets due to its strong malleability. Moreover, its ductility permits it to be pulled into wires without shattering.
• Low Melting Point: Tin has a relatively low melting point of about 232°C (449.6°F), which makes it easy to melt and cast. This property is particularly useful in applications like soldering.
• Corrosion Resistance: Tin is oxidation and corrosion-resistant, particularly in damp air. This makes it useful for applying rust-prevention coatings to other metals, including tin-plated steel food storage cans.
• Softness: Tin is a soft metal that bends and cuts easily. Although its softness restricts its structural applications, it can be used to improve the properties of other metals by alloying.
• Acoustic Properties: Tin can produce a characteristic sound known as “tin cry” when a bar of the metal is bent. This is caused by the deformation of the crystal structure and is unique to tin and some of its alloys.
• Alloy Formation: Tin and a wide range of other metals can easily create alloys. Two notable tin alloys are pewter (tin with antimony and copper) and bronze (tin with copper). These alloys are still in use now and have been significant historically.
• Non-toxicity: Tin is frequently used in the food sector for tin-plated cans and other containers since it is safe to come into contact with food and is not harmful.
• Electrical Conductivity: While not as conductive as metals like copper or silver, tin still has decent electrical conductivity, which makes it useful in electrical applications, particularly in solder for joining electrical components.
• Crystal Structure: At room temperature, tin is found in two primary allotropes: gray tin (alpha-tin), which is brittle and non-metallic, and white tin (beta-tin), which has a tetragonal crystal structure, which is the metallic form. Low-temperature tin can change from white to gray; this phenomenon is called “tin pest.”

Properties of Tin Metal

Physical Properties of Tin Metal

• Appearance: Tin is a silvery-white, lustrous metal.
• Density: At 7.31 grams per cubic centimeter, tin has a comparatively low density.
• Melting Point: Tin has a melting point of 231.93 degrees Celsius (449.47 degrees Fahrenheit).
• Boiling Point: Tin has a boiling point of 2,602 degrees Celsius (4,715.6 F).
• Malleability and Ductility: Tin metal is both malleable and ductile, which means it can be easily shaped and drawn into wires.
• Electrical Conductivity: While not as conductive as metals like copper and silver, tin metal is nevertheless a rather excellent conductor of electricity.
• Corrosion Resistance: Tin metal is resistant to corrosion from water but can be attacked by acids and alkalis.
• Sound Emission: The breakdown of the crystal structure when a bar of tin is bent results in the distinctive “tin cry” that is released.
• Thermal conductivity: Tin has a thermal conductivity of roughly 66.8 W/m·K, which is higher than many other materials but lower than that of metals such as copper.
• Crystal Structure: Tin can exist in two allotropic forms:
  • The metallic form of white tin, also known as β-tin, is stable at temperatures above room temperature. Its crystal structure is tetragonal.
  • A non-metallic type of tin that remains stable below 13.2 degrees Celsius (55.76 degrees Fahrenheit) is called gray tin, or α-tin. Its crystal structure is diamond cubic, just like that of germanium and silicon.

Chemical Properties of Tin Metal

The chemical properties of tin metal are discussed below:

Tin metal is usually unaffected by oxygen and water at ambient temperature. It doesn’t rust, corrode, or react in any other way. That explains why one of its primary use is to protect other metals by coating them. But when the metal reacts with oxygen and water (as steam) at higher temperatures, it turns into tin oxide.

Similar to this, tin metal is slowly destroyed by weak acids like sulfuric and hydrochloric acid. Dilute acids are made by dissolving small amounts of acid in large amounts of water. Tin’s properties make it an appropriate protective layer. Because it does not react with acids as quickly as many other types of metals, including iron, it can be used as a coating for other metals.

On the other hand, hot, concentrated alkaline solutions such as potassium hydroxide (KOH) and strong acids rapidly dissolve tin.

Sn₂ + KOH → K₂SnO₂ + H₂

Furthermore, the metal and halogens combine to form compounds such as tin bromide and tin chloride. It also produces tellurium, selenium, and sulfur in addition to other chemicals.

Reaction of Tin with Stannous Chloride

Tin(II) chloride, often known as stannous chloride, is the most important tin halide utilized in commerce. To show how these compounds are generated, SnCl₄ is produced when chlorine reacts with tin metal, whereas SnCl₂ and hydrogen gas are produced when tin metal and hydrochloric acid combine. Alternatively, SnCl₄ and Sn may combine to generate stannous chloride through a process called comproportionation.

SnCl₄ + Sn → 2SnCl₂

Reaction of Tin with Organometallic Compounds

Organotin compounds, also referred to as stannanes, are substances that contain tin-carbon bonds. These are the most profitable commercially available organic derivatives of tin compounds. Certain organotin compounds are toxic, despite the fact that they have been used as biocides.

Edward Frankland discovered diethyltin diiodide (C₂H₅)₂Sn₁₂ in 1849, and it was the first organotin compound to be characterized. The majority of organotin compounds are stable in the presence of water and air and exist as colorless liquids or solids. Tetrahedral geometry is employed. Tetraalkyl and tetraaryl, along with Grignard reagents, can be used to make tin compounds.

The mixed halide-alkyls are produced via redistribution techniques and are more widely utilized in commerce than tetraorgano derivatives:

SnCl₄ + R₄Sn → 2SnCl₂R₂

Tin Hydrides

In the +4 oxidation state of tin, stannane (SnH₄) becomes unstable. On the other hand, one of the most well-known organotin hydrides is tributyltin hydride (Sn(C₄H₉)₃. These compounds release short-lived tributyltin radicals, which are rare tin compounds (III).

Tin Electroplating

Tin-plating metals can be done in two ways. First, the metal that needs to be coated can be simply withdrawn after being dipped into the liquid, molten tin. Tin is a liquid that forms a thin coating on the base metal by adhering to it thinly and then cooling. The second method is electroplating. The base metal is suspended in a solution of tin sulfate or a similar material during the electroplating process. The base metal’s surface is coated with tin from the solution. due to the presence of an electric current within it.

A component of tin chloride is tin. When potassium permanganate (KMnO₄) and tin chloride mix, tin tetrachloride is produced. In this process, tin dichloride oxidizes, moving from a +2 to a +4 oxidation state.

SnCl₂+KMnO₄ → SnCl₄+Mn⁺²

When potassium dichromate and tin dichloride mix, tin tetrachloride and the Cr⁺³ cation are produced (green color).

SnCl₂+K₂CrO₇ → SnCl₄+Cr⁺³ (green colour) 

Uses of Tin metal

Tin is a versatile metal with a wide range of applications due to its physical and chemical properties. Here are detailed uses of tin:

• Tin metal plating: Tin metal is frequently used as a corrosion-prevention coating for other metals. This procedure, called “tin plating,” applies a thin layer of tin to copper and steel surfaces. Food cans are frequently made with tin coating, which helps stop corrosion and food contamination.
• Glass manufacturing: Tin compounds are important to the glass industry, especially tin dioxide (SnO₂). For low-emissivity (low-E) glass, tin dioxide is used as a transparent conducting oxide (TCO) layer. By reducing heat transfer through windows, Low-E glass helps to increase building energy efficiency. Buildings that have this improved capacity to reflect heat while letting in visible light have the potential to be more ecologically and energy-efficient. Tin compounds are necessary for contemporary glass coatings used in automotive and architectural settings.
• Optoelectronics: Tin metal is very useful in optoelectronics, especially when used as a constituent of sophisticated materials and gadgets. Thin tin dioxide (SnO₂) films, which are utilized in gas sensors to identify harmful gases and contaminants, are one prominent application. The particular alloying chemistry affects the films’ conductive or capacitive characteristics.
• Tin Foil: Before aluminum foil became common, tin foil was widely used for packaging. Today, tin foil is still used in certain applications where its specific properties are beneficial, although it has largely been replaced by aluminum foil.
• Dental Applications: Because tin is safe to use in the mouth and biocompatible, it is used in many dental applications. Tin metal is frequently used in dental amalgams, where it is an essential element along with silver, mercury, and other metals. Due to their affordability and longevity, dental amalgams have been utilized for more than a century; but, these days, more resilient and long-lasting polymer and ceramic alternatives frequently take their place. To stop tooth decay and lessen sensitivity, mouthwash and toothpaste also contain tin-based ingredients such stannous fluoride. They have antimicrobial qualities and build dental enamel.
• Ammunition: Tin metal is used in some types of ammunition, such as tin shot, which is an alternative to lead shot for hunting waterfowl. It reduces the environmental impact of lead contamination.
• Energy Storage: Tin is being investigated for application in cutting-edge energy storage technologies. One such technology is tin-based anodes for lithium-ion batteries, which may provide improved performance and increased capacity.
• Alloys
  • Bronze: Tin plays a significant role in bronze, an alloy mainly composed of copper and tin. Because of its endurance and hardness, bronze is used to make musical instruments, statues, and bearings.
  • Solder: Tin metal is a necessary component of solder, which is used in the electronics industry to connect electrical components. Although lead-free solders, which frequently contain tin, silver, and copper, are becoming increasingly popular due to environmental and health concerns, tin-lead solder has historically been used extensively.
  • Pewter: This alloy is used to make jewelry, tableware, and decorative items. It contains tin along with trace amounts of copper, antimony, and lead.
• Tin Chemicals
  • In dyeing operations, tin(II) chloride, also known as stannous chloride, is used as a mordant and reducing agent. Tin-plated steel is another product made with it.
  • Tannic oxide, also known as tin(IV) oxide, is used as a metal and glass polishing powder and as an opacifier in ceramic glazes.
  • Organotin Compounds: Used as catalysts in a variety of industrial processes, biocides, and stabilizers in PVC polymers. However, the use of several organotin compounds is restricted due to their toxicity.

Advantages of Tin Metal

• It can be used in situations where other metals would rust or corrode due to its exceptional resistance to corrosion. Under mild conditions, its corrosion rate is low even if its oxide layer is not oxygen-proof.
• The low melting point of pure tin (231.9 °C) is a feature that contributes to many of the alloys in which it is included.
• Tin gives many alloys their malleability. It can be utilized in many different ways and forms since it is simple to mold, roll, or draw into thin sheets or wires.
• Tin metal is used in solder and coatings, among other electrical and electronic components, since it conducts electricity. Although it has a lesser conductivity than copper, it is rarely used over wide conductivity gaps, resulting in extremely low net resistivity at any junction.
• Tin metal is safe to use in food packaging, medical equipment, and dental applications since it is biocompatible.
• Tin metal is easily miscible with several other metals to improve their qualities in alloys. These alloys include pewter, bronze, and babbitt metal.
• In optoelectronic devices such as solar cells and touch screens, tin dioxide (SnO₂) is employed as a transparent conducting oxide (TCO). It blends electrical conductivity and transparency.
• Using tin metal in goods like low-E glass can help make buildings more energy-efficient.
• Tin compounds are used in many industrial applications, such as paint pigments, stabilizers, and catalysts.

Disadvantages of Tin Metal

• Compared to many other metals, tin metal has extremely low tensile and shear strength, which renders it completely inappropriate for use in bulk structural applications.
• Tin metal is not a good choice for high-temperature applications due to its low melting point.
• Tin exhibits “tin pest,” or brittleness at low temperatures, which can cause structural problems in particular applications.
• Although tin is usually resistant to corrosion, it can corrode under some harsh conditions, especially when it comes into contact with strong acids and alkalis.
• Although tin metal is an excellent electrical conductor, it cannot be used as a long-path conductor since it is not as conductive as certain other metals like copper or silver.
• When tin is kept at high temperatures, it will gradually and quickly oxidize, which will eventually compromise its performance.

Side Effects of Tin on the Environment

Tin’s structure and unique qualities have a significant impact on the environment. A few of them consist of:

• Impact of Mining: Mining operations used to extract tin from its ore, usually cassiterite, have the potential to seriously deteriorate the environment. This includes actions that can harm nearby ecosystems, such as habitat degradation, soil erosion, and deforestation.
• Water Pollution: The extraction and processing of tin can contaminate nearby water supplies. Large volumes of water are frequently used in the process, which increases the risk of heavy metal and harmful chemical contamination. In addition to endangering aquatic life, this contaminated water is unfit for use in agriculture and human consumption.
• Air pollution: Sulfur dioxide and particulate matter are among the pollutants released into the atmosphere during the smelting and refining of tin. These emissions may be a factor in respiratory disorders in both people and animals, acid rain, and poor air quality.
• Soil Contamination: When mining waste is disposed of, the soil may get contaminated. Tin and other related heavy metals can build up in the soil, decreasing its fertility and turning it poisonous to plants and microbes. Both local agricultural and terrestrial ecosystems may be harmed by this.
• Acid Mine Drainage: During tin mining, sulfide mineral exposure may result in acid mine drainage. This process involves the reaction of sulfides with oxygen and water to generate sulfuric acid, which can further contaminate soil and streams by leaching heavy metals from the surrounding rock.
• Waste Production: Tailings and slag are among the many waste products produced throughout the tin mining and refining processes. These waste products may include heavy metals and leftover chemicals, which makes long-term management and disposal difficult.
• Ecological Disruption: Local ecosystems may be affected by the extensive disturbances brought on by tin mining operations. This covers the dispersal of wildlife, depletion of biodiversity, and modifications to land use practices.

References

• https://www.thoughtco.com/metal-profile-tin-2340157
• https://www.rsc.org/periodic-table/element/50/tin
• Ohn Emsley, Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, New York, 2nd Edition, 2011.
• https://byjus.com/chemistry/tin/
• https://www.lenntech.com/periodic/elements/sn.htm
• https://testbook.com/chemistry/tin