Metal

Metal is a shiny material.

It can carry heat. It can also carry power. This happens because tiny parts inside move easily.

Metals can be shaped. You can hammer them into new forms. You can even pull them into long wires. Some metals are very light. Others are very heavy. We use them for big bridges and fast cars.

Metal is a part of our world.

Metal is a special kind of material. Most metals are shiny when they are polished.

This shine happens because tiny parts called electrons move freely. These moving electrons also help metals carry heat and electricity.

Because of these electrons, metals are good conductors. A conductor is something that lets energy flow through it easily.

Metals are also very easy to shape. They are malleable, which means you can press them into shapes. They are also ductile, which means you can pull them into thin wires.

Some metals are very light, like magnesium. Others are very heavy, like osmium.

People have used metals for a long time. Humans used copper about 11,000 years ago. We also use metals to make alloys. An alloy is a mix of different metals. For example, stainless steel is an alloy made of iron, chromium, and nickel.

We use these strong materials for bridges, cars, and tools.

Metals are a special group of materials used in almost everything.

They are known for being shiny or lustrous when they are polished. This shine happens because electrons move freely within the material. These same electrons allow metals to carry heat and electricity very well.

Most metals are also easy to change into new shapes. They are malleable, which means they can be pressed or hammered. They are also ductile, meaning they can be pulled into thin wires.

How metals work depends on tiny particles called electrons. In metals, these electrons are available at the Fermi level. This means they can move into empty spaces easily. When you apply a voltage, these electrons shift and create an electric current.

This same movement helps heat travel through the metal. This process is called conduction. Most metals become less good at carrying electricity as they get hotter. This is because the atoms move more and get in the way.

Humans have worked with metals for many thousands of years. People began using copper about 11,000 years ago. Before the fifth millennium BCE, people used gold, silver, and lead. They also used iron that came from space, called meteoric iron.

Later, people learned how to make bronze. In 1809, scientists discovered sodium, which was the first light metal. Since World War II, we have made much more complex alloys.

There is a huge variety in how heavy metals are. Density tells us how much mass is in a certain space. Lithium is the least dense metal at 0.534 g/cm3. Osmium is the most dense at 22.59 g/cm3.

Some metals are much lighter than others. Magnesium and aluminum are important light metals used in many things. For example, aluminum has a density of 2.7 g/cm3. This is much lighter than iron, which is 7.9 g/cm3.

We see metals working all around us every day. Strong metals are used to build high-rise buildings and huge bridges. They are also used to make most cars and many tools.

You can find metals in your home appliances and even in pipes. Some metals are mixed together to make alloys like stainless steel. This alloy uses iron, chromium, and nickel to stay strong.

Even the coins in your pocket are made from metal elements. There are now at least 23 different elements used for coinage.

A metal is a material characterized by specific physical and chemical properties. When polished or fractured, metals often show a lustrous or shiny appearance. They are also excellent conductors of both electricity and heat. These characteristics are not accidental. They occur because metals have electrons available at the Fermi level. This means certain electrons are in a state where they can easily move and interact with energy.

A metal can be a single chemical element, like iron, or a mixture called an alloy, such as stainless steel. It can even be a molecular compound, like polymeric sulfur nitride.

The way metals conduct electricity is a result of their unique electronic structure. In most materials, electrons are stuck in specific energy levels. In metals, however, there are unoccupied, delocalized electron states near the highest occupied levels. When a voltage is applied, some electrons shift to states with slightly higher momentum in the direction of the electric field. This creates a net drift velocity, which we recognize as an electric current.

This conduction happens even at absolute zero because of these delocalized states. In contrast, semiconductors have an energy gap that prevents easy electron flow.

Metals also move heat very efficiently through a process called conduction. This heat is transported mainly by the conduction electrons. As these electrons gain kinetic energy, they can pass that thermal energy to other parts of the material. The Wiedemann–Franz law describes a relationship in many metals where the ratio of thermal conductivity to electrical conductivity is proportional to the temperature.

Generally, as a metal heats up, its electrical conductivity decreases. This happens because the increased thermal motion of the atoms makes it harder for the electrons to flow smoothly.

Physical shaping is another defining trait of metals, described by two terms: malleability and ductility. Malleable metals can be hammered or pressed into sheets. Ductile metals can be drawn out into thin wires.

This ability to deform without breaking is due to the nondirectional nature of metallic bonding. This allows for dislocation motion, where atoms can slide past one another. In many metals, the atoms are arranged in close-packed crystal structures. These include body-centered cubic (bcc), face-centered cubic (fcc), and hexagonal close-packed (hcp) structures.

There is a massive range in the density of different metals. Density measures how much mass is packed into a specific volume. Lithium is the least dense metal, with a density of only 0.534 g/cm3. On the other end of the scale, osmium is the most dense at 22.59 g/cm3.

Many industrial metals are chosen because they are lightweight. For example, aluminum has a density of 2.7 g/cm3, which is much lighter than iron at 7.9 g/cm3. Magnesium and titanium are also important light metals used in many modern applications.

The history of human interaction with metals spans many millennia. Humans likely began using copper about 11,000 years ago. Before the first bronze appeared in the fifth millennium BCE, people used gold, silver, lead, and even meteoric iron.

The discovery of sodium in 1809 marked the finding of the first light metal. Since the end of World War II, scientists have developed increasingly sophisticated alloys for specialized uses.

Today, metals are essential to almost every aspect of modern civilization. Their strength and resilience make them vital for high-rise buildings and large bridges. They are used to construct vehicles, tools, pipes, and railroad tracks.

In the electronics industry, multi-element metals like titanium nitride are used in semiconductors. Even our money relies on them; modern coinage includes at least 23 different chemical elements. From the stainless steel in a gravy boat to the heavy structural steel in a skyscraper, metals shape our world.