Iron oxide

Iron and air can join to make something new.

This is often called rust.

These things are found all over the Earth. They can be in the ground. They can even be in living things.

People use them to make paint. These paints have many colors. They can be red, yellow, or black.

Some of these colors are very cheap. They are also safe to use. Long ago, people used them for cave art.

It is amazing to see these colors in nature.

Iron oxide is a compound made of iron and oxygen.

This material is found all over our world. It is in the ground and in living things. Some iron oxides are called ferric oxyhydroxides. Rust is the most famous type.

People use iron oxide as a pigment. A pigment is a substance used to add color. These pigments come in colors like red, yellow, and black. They are cheap and safe to use. Long ago, people used them for cave art.

Iron oxides are also very useful in industry. Factories use them to make iron metal. They use carbon to help this change happen. Magnetite is a special type of iron oxide. It is used in magnetic recording tapes. Some iron oxides are even used in food. We call this food coloring E172. In living things, iron is kept in a form called ferritin. This helps store iron inside organisms.

Iron oxide is a compound made of iron and oxygen. It is found all over the Earth and in many living things. There are several different types of iron oxides in nature. Some are known as ferric oxyhydroxides. Rust is the most famous member of this group.

These materials play a big role in many geological and biological processes. They are very important to the way our world works.

Different iron oxides have different names and structures. Some contain iron in a state called ferrous, which is Fe(II). Others contain iron in a ferric state, known as Fe(III).

A few important types found on the Earth's surface are wüstite, magnetite, and hematite. Magnetite is a mixed oxide of both ferrous and ferric iron. Other types like goethite are called oxide-hydroxides. These materials can change when they lose water.

Humans have used these substances for a very long time. In the 15,000s BC, people used iron oxide for cave art in parts of Asia. They used it as a pigment without any other glue to hold it.

Today, we use iron oxides as inexpensive and durable pigments. They add colors like red, yellow, orange, brown, and black to paints. They are also used in colored concrete and coatings. Some are even used as a food coloring called E172.

Iron oxides are also used in many big industries. Most iron ores are oxides, so they are used to make iron metal. Factories use a reducing agent like carbon to turn these oxides into metal.

Magnetite is a special type used in magnetic recording tapes. Some iron oxides are even used in a process called thermite. They can also act as catalysts to help other reactions happen. These many uses make them very important to modern life.

Nature uses iron oxide in amazing ways too. Some bacteria, like Shewanella oneidensis, use these oxides to help them live.

Inside living things, iron is stored in a form called ferritin. This is a ferrous oxide kept inside a special protein sheath. This is similar to how your body stores important supplies for later. It shows how much iron oxide is part of life itself.

Iron oxide is a chemical compound made of iron and oxygen. These compounds are widespread throughout the natural world. They play vital roles in many geological and biological processes. Iron oxides are also used as iron ores to create metal. They serve as pigments, catalysts, and ingredients in thermite.

Even our own bodies use these materials. For example, iron occurs in hemoglobin. Because they are so versatile, they are important to both nature and human industry.

To understand these compounds, we must look at their chemical structure. Many iron oxides are non-stoichiometric. This means the ratio of iron to oxygen atoms is not always a simple whole number. Iron can exist in different oxidation states. These states are called ferrous, which is Fe(II), and ferric, which is Fe(III).

Some compounds contain only one type, while others contain a mixture of both. These atoms arrange themselves into specific geometric shapes. They adopt either octahedral or tetrahedral coordination geometry to form their structures.

There are several distinct types of iron oxides found on Earth. Only a few are significant at the Earth's surface. Wüstite is an oxide of Fe(II), known as FeO. Hematite is an oxide of Fe(III), known as Fe2O3. There is also a mixed oxide called magnetite, which is Fe3O4. Magnetite contains both ferrous and ferric iron.

Other forms of Fe2O3 include alpha, beta, gamma, and epsilon phases. There are also oxide-hydroxides, such as goethite and lepidocrocite. These are related to the class of compounds known as ferric oxyhydroxides.

Humans have utilized these minerals for thousands of years. The earliest recorded uses were for decoration. In the 15,000s BC, people in parts of Asia used iron oxide for cave art. At that time, they used the pigment without any adhesive agent to hold it to the surface.

Today, we use them as inexpensive and durable pigments. They provide colors in the earthy range, including yellow, orange, red, brown, and black. They are used in paints, coatings, and colored concrete. Some are even used as a food coloring labeled E172.

In modern industry, iron oxides are essential for making metal. Almost all iron ores are oxides. This makes them necessary precursors to iron metal and various alloys. In blast furnaces and related factories, these oxides are converted into metal. This process requires a reducing agent, such as various forms of carbon.

This chemical change allows us to turn raw ore into the strong metal used in construction and tools.

Specific properties make certain oxides very useful for technology. Magnetite is a component used in magnetic recording tapes. Iron oxides also have specific rates of thermal expansion. For example, the coefficient of thermal expansion for Fe2O3 is 14.9 x 10⁻⁶ °C⁻¹. The value for FeO is 12.1 x 10⁻⁶ °C⁻¹. Magnetite has a value greater than 9.2 x 10⁻⁶ °C⁻¹. These measurements are important for engineers who use these materials in different environments.

Biology also relies on the chemistry of iron. In many organisms, iron is stored in a form called ferritin. This is a ferrous oxide that is encased in a solubilizing protein sheath.

Certain species of bacteria also interact with these compounds. Bacteria such as Shewanella oneidensis, Geobacter sulfurreducens, and Geobacter metallireducens use iron oxides as terminal electron acceptors. This shows how iron oxide is deeply connected to the cycles of life and the movement of electrons in the natural world.