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Aluminium

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What Is Aluminium?

Aluminum (Al), also written aluminium, is a light silvery white metal in the periodic table's major Group 13 (IIIa, or boron group). Aluminum is the most abundant metallic element (the aluminium element) in the Earth's crust and the most prevalent nonferrous metal. Aluminum is never found in its metallic form in nature due to its chemical activity, but its compounds can be found to various extents in almost all rocks, vegetation, and animals.

The aluminum atomic number is 13, the aluminium symbol is Al and Al chemical name. Let us look at more detailed information on the aluminium structure, uses properties and compounds and more from this article.

Physical and Chemical Properties

Aluminum, with the aluminium symbol, Al, is concentrated in the outer 16 km (10 miles) of the Earth's crust, where it makes up around 8% of the total weight; only oxygen and silicon come close. Aluminum is derived from the Latin word alumen, which refers to potash alum (KAl(SO4)212H2O), also known as aluminium potassium sulphate.

The Chemical Properties of Aluminum Are as Follows.

Aluminum atomic number

13

Atomic weight

26.9815384

Melting point

660°C (1,220 °F)

Boiling point

2,467 °C (4,473 °F)

Specific gravity

2.70 (at 20 °C [68 °F])

Valence 

3

Electron configuration

1s22s22p63s23p1

Al chemical name

Aluminum


Aluminium Structure

The aluminium structure is represented below.

(image will be updated soon)

Occurrence and History

Aluminum is found as aluminosilicates in feldspars, feldspathoids, and micas in igneous rocks; as clay in soil generated from them; and as bauxite and iron-rich laterite after further weathering. The main aluminium resource is bauxite, which is a combination of hydrated aluminium oxides. Emery (corundum) is a crystalline aluminium oxide found in a few igneous rocks that is mined as a natural abrasive or in finer forms as rubies and sapphires. Other gemstones that include aluminium include topaz, garnet, and chrysoberyl. Alunite and cryolite are some of the many other aluminium minerals that have commercial use.

People in Mesopotamia were manufacturing beautiful pottery from an aluminium compound clay before 5000 BCE, while Egyptians and Babylonians used aluminium compounds in various chemicals and medicines about 4,000 years ago. Pliny refers to alumen, now known as alum, an aluminium compound widely used to fix dyes in fabrics in the ancient world. Chemists like Antoine Lavoisier recognised alumina as a potential metal source in the latter half of the 18th century.

Danish physicist Hans Christian Oersted obtained crude aluminium in 1825 by reducing aluminium chloride with potassium amalgam. Sir Humphry Davy, a British chemist, had already termed the aluminium element after electrolyzing fused alumina (aluminium oxide) and had made an iron-aluminum alloy in 1809; the word was eventually adjusted to aluminium in England and some other European countries. Using potassium metal as a reducing agent, German chemist Friedrich Wöhler created aluminium powder (1827) and tiny globules of the metal (1845), from which he was able to discover some of its properties.

The public first saw the new metal (1855) during the Paris Exposition, around the same time that it became available (in small quantities at a high cost) through the sodium reduction of molten aluminium chloride via the Deville process.

When electricity became more readily accessible and cheap, Charles Martin Hall in the United States and Paul-Louis-Toussaint Héroult in France almost simultaneously discovered (1886) the modern method of commercially producing aluminium: electrolysis of purified alumina (Al2O3) dissolved in molten cryolite (Na3AlF6). During the 1960s, aluminium replaced copper as the world's leading producer of nonferrous metals.

This is the detailed information on the occurrence and history of aluminium.

Uses of Aluminium and Properties

The uses, properties and compounds of aluminum are explained here.

Small amounts of aluminium are added to certain metals to improve their qualities for specific uses of aluminium, such as aluminium bronzes and most magnesium-base alloys; or moderate amounts of other metals and silicon are added to aluminium in aluminum-base alloys. Aircraft construction, building materials, consumer durables (refrigerators, air conditioners, kitchen utensils), electrical conductors, and chemical and food-processing equipment all utilize the metal and its alloys.

Commercial aluminium (99 to 99.6% pure) with modest concentrations of silicon and iron is robust and strong; pure aluminium (99.996%) is soft and weak. Aluminum is a ductile and malleable metal that may be drawn into wire or rolled into thin foil. The metal has a density of about one-third that of iron or copper. Aluminum is highly corrosion-resistant, while being chemically active, because it creates a thick, strong oxide film on its surface when exposed to air.

Aluminum is a great heat and electrical conductor. It has half the heat conductivity of copper and two-thirds the electrical conductivity. It forms a face-centered cubic aluminium structure when it crystallises. Aluminum-27 is the stable isotope of all natural aluminium. Aluminum oxide and hydroxide, as well as metallic aluminium, are nontoxic.

Most dilute acids attack aluminium slowly, while concentrated hydrochloric acid dissolves it quickly. Concentrated nitric acid, on the other hand, may be transferred in aluminium tank cars since it neutralises the metal. Alkalies such as sodium and potassium hydroxide attack even very pure aluminium to produce hydrogen and the aluminate ion. Finely divided aluminium will burn in carbon monoxide or carbon dioxide with the development of aluminium oxide and carbide if ignited, however aluminium is inert to sulphur at temperatures up to red heat due to its high affinity for oxygen.

By using emission spectroscopy, aluminium can be detected in quantities as low as one part per million. Aluminum can be quantified as an oxide (aluminum formula Al2O3) or as a derivative of the organic nitrogen compound 8-hydroxyquinoline (aluminum formula 8-hydroxyquinoline). Al(C9H6ON)3 is the molecular aluminum formula of the derivative.

Compounds

Aluminum is generally trivalent. However, a few gaseous monovalent and bivalent compounds have been produced at high temperatures (AlCl, Al2O, AlO). The configuration of the three outer electrons in aluminium is such that the bare ion, Al3+, generated by the loss of these electrons is known to occur in a few compounds (e.g., crystalline aluminium fluoride [AlF3] and aluminium chloride [AlCl3]).

However, because the energy required to form the Al3+ ion is so large, it is usually more energy efficient for the aluminium atom to form covalent compounds via sp2 hybridization, as boron does. Hydration can stabilise the Al3+ ion, and the octahedral ion [Al(H2O)6]3+ can be found in aqueous solution and in a variety of salts.

A multitude of aluminium compounds are used in a wide range of industries. Alumina, which is found naturally as corundum, is also mass-produced in enormous amounts for use in aluminium metal, insulators, spark plugs, and other products. Alumina develops a porous aluminium structure when heated, allowing it to absorb water vapour. This type of aluminium oxide, known as activated alumina in the industry, is used to dry gases and liquids. It also acts as a carrier for numerous chemical reaction catalysts.

FAQs on Aluminium

1. What is Aluminium and what are its key physical properties?

Aluminium (symbol: Al) is a chemical element with atomic number 13, located in Group 13 of the periodic table. It is the most abundant metal in the Earth's crust. Its key physical properties include:

  • Lightweight: It has a low density, making it ideal for applications where weight is a concern.
  • High Strength-to-Weight Ratio: Despite being light, it can be very strong, especially when alloyed.
  • Ductility and Malleability: It can be easily drawn into wires (ductile) or hammered into thin sheets (malleable), like aluminium foil.
  • Excellent Conductivity: It is a great conductor of both heat and electricity.
  • Lustrous Appearance: It has a silvery-white, shiny appearance.

2. Is Aluminium classified as a metal or a non-metal?

Aluminium is unequivocally a metal. It is specifically classified as a post-transition metal. Its metallic character is confirmed by its properties such as high electrical and thermal conductivity, metallic lustre, malleability, and ductility. Chemically, it tends to lose its three valence electrons to form a positive ion (Al³⁺), a characteristic behaviour of metals.

3. What are some important real-world uses of Aluminium?

Aluminium's unique properties make it useful in a wide range of applications. Some important examples include:

  • Transportation: Used extensively in manufacturing aircraft, automobiles, and railway coaches due to its low density and high strength.
  • Packaging: Commonly used for making beverage cans and flexible packaging like aluminium foil because it is non-toxic and provides a barrier against light and oxygen.
  • Construction: Used for window frames, roofing, and structural components in modern buildings.
  • Electrical Engineering: Utilised in high-voltage power transmission lines as a lightweight and cost-effective alternative to copper.
  • Consumer Goods: Found in everything from smartphone bodies and laptops to cooking utensils and furniture.

4. Why is Aluminium commonly used for making cooking utensils and foil?

Aluminium is a preferred material for cooking utensils and foil primarily because it is an excellent conductor of heat, which allows for even and efficient cooking. More importantly, when exposed to air, it forms a thin, tough, and invisible layer of aluminium oxide (Al₂O₃) on its surface. This process, called passivation, makes the underlying metal resistant to corrosion and prevents it from reacting with acidic or alkaline foods, ensuring it is safe for food contact.

5. What does the electronic configuration of Aluminium (Z=13) reveal about its chemical behaviour?

The electronic configuration of Aluminium is 1s² 2s² 2p⁶ 3s² 3p¹. This configuration is key to understanding its chemistry:

  • It shows that Aluminium has three valence electrons (the two in the 3s orbital and one in the 3p orbital).
  • To achieve a stable, noble gas configuration, Aluminium readily loses these three electrons.
  • This tendency to lose electrons makes it a reactive metal that typically forms a +3 oxidation state by creating the cation Al³⁺.

This behaviour defines its electropositive character and its role in forming ionic and covalent compounds.

6. Why does Aluminium resist corrosion despite being a highly reactive metal?

The resistance of Aluminium to corrosion is a classic example of passivation. Although Aluminium is intrinsically very reactive, upon exposure to oxygen in the air, it instantly forms a very thin, dense, and non-porous protective layer of aluminium oxide (Al₂O₃). This inert oxide layer adheres strongly to the metal surface, sealing it off from the surrounding environment (air, water) and effectively preventing any further oxidation or corrosion. This is why aluminium surfaces remain bright and do not rust like iron.

7. How does Aluminium's reaction with both acids and alkalis classify its chemical nature?

Aluminium's ability to react with both acids and strong alkalis (bases) demonstrates that it has an amphoteric nature. This means it can behave as both an acid and a base.

  • Reaction with Acid (e.g., HCl): It acts as a typical metal, liberating hydrogen gas.
    2Al(s) + 6HCl(aq) → 2AlCl₃(aq) + 3H₂(g)
  • Reaction with Alkali (e.g., NaOH): It reacts to form a salt and liberates hydrogen gas.
    2Al(s) + 2NaOH(aq) + 6H₂O(l) → 2Na[Al(OH)₄](aq) + 3H₂(g)

This dual reactivity is a key chemical characteristic of Aluminium, distinguishing it from many other metals.

8. What is the difference between the spellings 'Aluminium' and 'Aluminum'?

Both spellings are correct but used in different regions. 'Aluminium' is the internationally recognised spelling established by the International Union of Pure and Applied Chemistry (IUPAC) and is standard in the United Kingdom, India, and most of the world. 'Aluminum' is the common spelling used in the United States and Canada. The difference is simply a matter of regional linguistic preference and does not refer to different substances.