What Is Iron?
\[Fe_{3}O_{4}\], the chemical name Iron (II, III) oxide, occurs as a mineral. \[Fe_{3}O_{4}\] is a rare mineral that also occurs naturally as the mineral known as hematite. The mineral is a brownish to greyish or black stone, iron-like structure, also known as Magnetite or Magnetic oxide. It holds a characteristic metallic or a greasy lustre and is not transparent.
It comprises both \[Fe^{2+}\] and \[Fe^{3+}\] ions and is at times formulated as \[\textrm{FeO}\] ∙ \[Fe_{3}O_{4}\].
A Brief On \[Fe_{3}O_{4}\] Structure
Iron (II, III) oxide holds a cubic inverse spinel group structure. The \[Fe_{3}O_{4}\] structure comprises a cubic system, a close-packed array of oxide ions, in which all of the \[Fe^{2+}\] ions are present on one-half of the octahedral sites. At the same time, the \[Fe^{3+}\] are split evenly across the remaining tetrahedral sites and octahedral sites.
Both \[\gamma\] - \[Fe_{3}O_{3}\] and \[\textrm{FeO}\] hold a similar cubic structure with a close packed array of oxide ions. This packing leads to ready interchangeability between the three compounds through the oxidation and reduction process—these reactions leave a relatively small change to the structure of the compound.
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Iron (II, III) oxide exhibits ferrimagnetism due to the electron spins of the \[\textrm{Fe}\]-II and \[\textrm{Fe}\]-III ions. As a result, these ions undergo coupling in the octahedral sites, and the reels of the \[\textrm{Fe}\]-III ions present in the tetrahedral sites remain coupled but are anti-parallel to the former.
The total effect of the overall process is that the magnetic contributions of both sets of ions are not balanced, thus leading to a permanent magnetism.
Experimentally constrained models to display that the iron ions remain coordinated to the five oxygen ions on average when in the molten state. Furthermore, there is a distribution of coordination sites in the liquid form. The minority populations of both 4- and 6-fold coordinated Iron, and most \[\textrm{Fe}\]-II and \[\textrm{Fe}\]-III are 5-coordinated to oxygen.
What Is the \[Fe_{3}O_{4}\] chemical name?
\[Fe_{3}O_{4}\] is the chemical name of a compound called Magnetite, which is the mineral of Iron. The mineral holds the most magnetic property of all the naturally-occurring minerals occurring on Earth. The \[Fe_{3}O_{4}\] chemical name of the mineral is Iron(ll, lll) oxide as per IUPAC is known as ferrous-ferric oxide.
\[Fe_{3}O_{4}\] reaction
Iron (ll, lll) oxide is obtained through a series of chemical reactions-
Steel production process: The steel production process is a process that occurs through the reduction of the magnetite ore by carbon monoxide. This reaction takes place in a blast furnace and gives the following response:
\[Fe_{3}O_{4}\] + \[4CO\] \[\rightarrow\] \[\textrm{3Fe}\] + \[4CO_{2}\]
Production of the brown pigment: Brown pigment is a by-product that occurs when the mineral magnetite undergoes controlled oxidation. This reaction leads to the production of quality γ-\[Fe_{3}O_{4}\]. The reaction takes place as follows:
\[2Fe_{3}O_{4}\] + \[\frac{1}{2}O_{2}\] \[\rightarrow\] \[3\gamma\] \[Fe_{3}O_{4}\]
(Magnetite) (Maghemite)
Production of the red pigment: Red pigment is a by-product that occurs when the Magnetite undergoes vigorous calcining. This reaction leads to the production of a quality α-\[Fe_{3}O_{4}\]. The reaction takes place as follows:
\[2Fe_{3}O_{4}\] + \[\frac{1}{2}O_{2}\] → 3 \[\alpha\] - \[Fe_{3}O_{3}\]
(Magnetite) (Hematite)
Introduction To \[Fe_{3}O_{4}\] Nanoparticles
Iron oxide nanoparticles are iron oxide particles that differ in diameters between about one and 100 nanometers. Magnetite occurs in two predominant forms, and the oxidized form of the mineral is called maghemite \[(\gamma - Fe_{3}O_{3})\].
Iron oxide nanoparticles hold superparamagnetic properties that have drawn extensive interest leading to potential applications in multiple fields.
Iron oxide nanoparticles, ferrimagnetic maghemite, comprise \[Fe^{3+}\] vacancies, while the ferrimagnetic Magnetite contains \[Fe^{2+}\] and \[Fe^{3+}\] vacancies.
The composition of these two elements gives the compound biocompatibility, biodegradability, and the possibility to tailor magnetic behaviour, leading to an extensive application in medicine.
However, the nanoparticle size, aggregation, electronic, and magnetic properties significantly influence the biological effect of the compound.
The magnetic targeting iron nanoparticles commonly serve as a podium for attaching drugs like doxorubicin (DOX). However, their primary application is in tumour therapy, resulting in oxidative stress and hyperthermia, leading to tumour cell damage.
Synthesis Of Iron Oxide Nanoparticles
The preparation process of Iron oxide nanoparticles significantly affects the size, distribution, shape, and surface chemistry of the particles. The nanoparticles also determine to a great extent the type of structural defects or impurities, or distribution in the nanoparticles.
However, multiple factors affect magnetic behaviour. As a result, there are many recent attempts to develop techniques and processes that yield "monodisperse colloids" consisting of nanoparticles in a structured uniform in size and shape.
Coprecipitation
The employed method, by far, is coprecipitation, which is of two types. The first batch of ferrous hydroxide suspensions undergoes partial oxidation with different oxidizing agents. For example, the spherical magnetite particles have a narrow size distribution consisting of mean diameters ranging from 30 to 100 nm. This process can be obtained from a Fe(II) salt, a mild oxidant (nitrate ions), and a base.
The other common method for this process occurs through the ageing stoichiometric mixtures of ferrous and ferric hydroxides in aqueous media. This process leads to the yielding spherical magnetite particles that are homogeneous in size. In this method, the following chemical reaction occurs as follows-
\[2Fe^{3+}\] + \[Fe^{2+}\] + \[8OH\] → \[Fe_{3}O_{4}\] + \[4H_{2}O\]
The optimum conditions for this reaction occur between a pH 8 and 14, with the \[Fe^{3+}\] or \[Fe^{2+}\]
ratio being 2:1 and a non-oxidizing environment. This reaction is highly susceptible to oxidation. Thus the compound magnetite gets transformed to maghemite in the presence of oxygen.
\[2Fe_{3}O_{4}\] + \[O_{2}\] → \[2\gamma\] \[Fe_{3}O_{3}\]
The shape and size of the Iron oxide nanoparticles can be manually controlled by adjusting physical factors such as the nature of the salts (perchlorates, chlorides, sulfates, and nitrates), pH, temperature, ionic strength, or the \[\frac{Fe(II)}{Fe(III)}\] concentration ratio.
Microemulsions
A microemulsion is a stable isotropic dispersion of two immiscible liquids. Microemulsions consist of nanosized domains of either one or both liquids of a stabilized interfacial film medium of surface-active molecules.
Microemulsions are further categorized as oil-in-water or water-in-oil, depending on the continuous and dispersed phases. Water-in-oil is the most popular combo for the synthesis action of many kinds of nanoparticles.
The water and oil components are mixed with an amphiphilic surfactant that lowers the surface tension between water and oil, thus, making the solution transparent. The water nanodroplets in this process act as nanoreactors for synthesizing nanoparticles.
The shape of the water pool is spherical, and the nanoparticles' size also depends on the size of the water pool, which enables the size of spherical nanoparticles to be tuned as per the size change of the water pool.
High-temperature decomposition of organic precursors
In the presence of hot organic surfactants, iron precursors lead to deterioration resulting in samples that hold a reasonable size control, good crystallinity, and narrow size distribution (5-12 nm), due to which the nanoparticles are easily dispersed.
The size of the particles plays a crucial role in instances of biomedical applications like magnetic resonance imaging, magnetic cell separation or magnetorelaxometry, and the magnetic nanoparticles produced by the method of high-temperature decomposition of organic precursors are very useful.
The most viable iron precursors in organic solvents include \[Fe (CUP)_{3}\], \[Fe (CO)_{5}\], or \[Fe (acac)_{3}\] that consists of surfactant molecules. A combination of Xylenes and Sodium Dodecylbenzene Sulfonate used as a surfactant commonly creates nanoreactors that lead to well-dispersed Iron (II) and Iron (III) salts to react.
FAQs on Iron
1. Why is the chemical symbol for iron 'Fe'?
The symbol 'Fe' for iron originates from its Latin name, 'ferrum'. In chemistry, many elements that have been known since ancient times have symbols derived from their classical names rather than their modern English ones. This convention helps maintain a universal standard across different languages.
2. What are the most important industrial uses of iron?
Iron is arguably the most important metal in modern industry due to its strength and abundance. Its primary uses include:
- Steel Production: The vast majority of iron is used to make steel, an alloy used in construction, automobiles, ships, and appliances.
- Structural Engineering: As reinforced concrete and structural beams, it forms the skeleton of bridges, skyscrapers, and other large-scale infrastructure.
- Manufacturing: It is essential for creating industrial machinery, tools, engine parts, and railway tracks.
- Cast Iron Products: Used for making pipes, engine blocks, and decorative items due to its excellent casting properties.
3. Why does iron exhibit variable oxidation states, such as +2 and +3?
Iron exhibits variable oxidation states because the energy difference between its 4s and 3d orbitals is very small. It can easily lose its two outermost 4s electrons to form the ferrous ion (Fe²⁺). Subsequently, it can lose one more electron from its 3d orbital to attain a highly stable, half-filled d-orbital configuration (3d⁵), forming the more stable ferric ion (Fe³⁺). This energetic feasibility allows iron to participate in reactions using different numbers of electrons.
4. How does its electronic configuration explain why iron compounds are often coloured and paramagnetic?
The chemical properties of iron compounds are directly linked to its d-orbital electrons:
- Coloured Compounds: Iron ions (Fe²⁺/Fe³⁺) in compounds have partially filled d-orbitals. When visible light passes through them, electrons absorb energy of a specific colour to jump to a higher energy d-orbital, a process called d-d transition. The compound displays the complementary colour of the light absorbed.
- Paramagnetism: This property arises from the presence of unpaired electrons. Both Fe²⁺ (4 unpaired electrons) and Fe³⁺ (5 unpaired electrons) have unpaired electrons that act like tiny magnets, causing them to be attracted to an external magnetic field.
5. What is magnetite (Fe₃O₄) and why is it classified as a mixed oxide?
Magnetite (Fe₃O₄) is a common iron ore known for its magnetic properties. It is classified as a mixed oxide because it contains iron atoms in two different oxidation states simultaneously. Its chemical structure is more accurately represented as a composite of iron(II) oxide (FeO) and iron(III) oxide (Fe₂O₃). Therefore, its formula can be written as FeO·Fe₂O₃, showing it contains both Fe²⁺ and Fe³⁺ ions.
6. Explain the chemical role of iron as a catalyst in the Haber-Bosch process.
In the Haber-Bosch process for ammonia synthesis, finely divided iron functions as a heterogeneous catalyst. It provides an active surface on which reactant gases (N₂ and H₂) can adsorb. This interaction weakens the extremely strong triple bond in the nitrogen molecule (N≡N), significantly lowering the activation energy of the reaction. This allows ammonia to be produced efficiently at lower temperatures and pressures than would otherwise be feasible.
7. What is the fundamental principle of extracting iron in a blast furnace?
The extraction of iron in a blast furnace is based on the principle of chemical reduction at high temperatures. Iron ore, primarily hematite (Fe₂O₃), is heated with coke (a form of carbon) and limestone (CaCO₃). The coke burns to produce carbon monoxide (CO), which acts as the main reducing agent. The carbon monoxide removes oxygen from the iron oxide, reducing it to molten iron in the key reaction: Fe₂O₃(s) + 3CO(g) → 2Fe(l) + 3CO₂(g).
8. What is the key difference between cast iron, wrought iron, and steel?
The primary difference between these three forms of iron lies in their carbon content, which dictates their physical properties:
- Cast Iron: Has a high carbon content (2-4%). It is hard and brittle but easy to cast into shapes.
- Wrought Iron: Contains very little carbon (<0.08%). It is the purest commercial iron, making it tough, malleable, and easy to weld.
- Steel: Has a carbon content between the other two (0.1-1.5%). This balance allows its properties, such as hardness and ductility, to be precisely controlled, making it the most versatile and widely used of the three.
9. What is the specific chemical function of the iron ion in haemoglobin?
In haemoglobin, the central component is an iron(II) ion (Fe²⁺) located within a heme group. The specific function of this Fe²⁺ ion is to act as the binding site for oxygen. It can form a reversible coordinate bond with an oxygen molecule (O₂) in the high-oxygen environment of the lungs. This bond is stable enough to transport oxygen through the blood but weak enough to be released to body tissues where oxygen levels are lower, enabling cellular respiration.
