The Science of Metals

Written by Lew Amicone

Metal is a lustrous material that conducts electricity and heat. You can probably point out multiple items made of metal around you because learning how to extract these metals and turn them into all kinds of other materials was an important development for human civilization. Even so, "metal" is a broad term that encompasses a variety of different kinds of materials, from lead, which is incredibly heavy, to aluminum, which is very light, and even mercury, which is most commonly seen as a liquid.

• What Is Thermal Conductivity? This article offers an overview of how to determine the rate at which heat can move through a material. Metals are generally good conductors.
• Material Science and Engineering Metals A short guide from the University of Washington offers a brief overview of the definition of metals.
• Metal Elements and the Periodic Table This page has an overview of metals and the different kinds of metals that grace the periodic table.

What Are Metals?

Metals are chemical elements that make up more than three quarters of the naturally occurring chemical elements on Earth. Often, metals are thought of as solids with relatively high melting points that are strong, shiny, good conductors of heat and electricity, and easy to work into different shapes. While that is generally true, metals can also encompass semi-metals or metalloids, which are elements with chemical and physical properties somewhere between metals and nonmetals, such as arsenic, boron, and antimony. The periodic table shows how we classify metals by setting them up in sections alongside other metals like them, such as the alkali metals, alkaline earth metals, transition metals, poor metals, and semi-metals.

• Metal Facts: Here is a slideshow full of information and facts about metal that you may not know.
• Science Basics: Metals: This article has an easy-to-follow overview of metals, alloys, and mining metal.
• Metals and Nonmetals: Check out a visual overview of the differences between metals and nonmetals.
• Parts of the Periodic Table: This article includes a breakdown of the different parts of the periodic table.
• Alkali Metals: Alkali metals are just one group of metals in the periodic table.
• Properties of Metals, Nonmetals, and Metalloids: Look at this slideshow to find an easy breakdown of pictures and details of metals and nonmetals.

Not-Quite Metals

There are plenty of metal-like materials used in everyday life that are actually alloys. Alloys are substances created by mixing at least one metal with other materials that may or may not be metals. For example, steel is an alloy of iron that contains a small amount of carbon. Plastics can also be combined with metal. They're sometimes electroplated, or coated in a thin layer of a metal element using electricity, to make them look like shiny metal. Plastics that have been electroplated look great and are cheaper and rustproof, but they are not durable.

• Alloys: This educational insert offers a brief overview of alloy materials and structures.
• Nickel Alloys: The Nickel Institute explains different types of metals that are created when nickel alloys with other materials.
• Aluminum Alloys 101: The Aluminum Association lists facts about what can be created when aluminum alloys with other materials.
• Electroplating Organic Materials: Learn what electroplating is and how it works here.

How Are Metals Made?

Metals are naturally occurring, but they aren't usually found in the ground exactly the way you'd expect to see them. They are usually buried deep within rocks with small deposits of other metals and exist as oxides rather than pure elements. Producing large quantities of metals requires extracting an ore from a mine or quarry and then refining the ore to get the metal into its pure form.

• Metal Oxide Aerogels: This page offers a detailed overview of metal oxide aerogels, how they can get their colors, and how they are prepared.
• Where Do Metals Come From? Find out where we get the metals people use every day with this simple explanation.
• What Are Minerals and Metals? The International Council on Mining & Metals explains what minerals and metals are and how they're naturally occurring.

What Are Metals Like?

Physical Properties

It's hard to generalize the properties of metal since they are all so different, but they do tend to have some common characteristics:

• They are mostly solid, crystalline, strong, and dense.
• They are malleable and ductile, but they don't wear out or break easily except after repeated stresses and strains due to metal fatigue.
• They are opaque and shiny and most commonly silvery gray in color.
• They conduct electricity well and feel cold to the touch.
• A List of Metals: This page offers a more detailed look at the properties of metals and the common characteristics that many of them share.
• Learn All About the Properties of Metals: Follow along with this lesson guide that describes the properties and categories of metals, alloys, metal from ore, and the corrosion process.
• How to Make Metals Stronger Try a fun science experiment to learn about the differences in hardness between different metals and how to make a metal stronger.

How Do Metals Conduct Heat and Electricity?

Metals are good conductors of heat and electricity because the atoms in metals arrange themselves in a structure that lets electrons move around and between them freely, carrying heat or electrical energy.

• Thermal Properties of Metals: This article has a visual overview of each metal and its conductivity rate as well as formulas for thermal conductivity conversions.
• Factors Influencing Electrical Conductivity: Learn more about the conductivity of metals and what can alter a material's conductivity.

What Is the Band Theory?

Scientists who study and work with metals, called metallurgists, explain the properties of metal using an idea called band theory. Band theory states that the atomic orbitals in a solid overlap to create bands that carry through the entire solid. There are two bands: the valence band, which contains electrons involved in bonding, and the conduction band, which allows electrons to carry heat or electrical energy freely through a metal. The way the electrons move through the bands is what distinguishes metals, nonmetals, and semi-metals.

• In metals, the two bands overlap, and heat or electric energy added to the material easily pushes electrons from the valence band to the conduction band, allowing conduction of heat or electricity.
• In nonmetals, there is a gap between the valence and conduction bands, so it takes a lot of energy to get an electron from one band to the other. This means that it's much harder for electrons to move into the conduction band, so the material doesn't readily conduct electricity or heat.
• Semi-metals are midway between metals and nonmetals; they are effectively insulators, but they have a lower band gap than most nonmetals.

Chemical Properties

Metals react well with other elements because their atoms give up electrons to form positive ions and compounds called salts. In fact, the salt you may add to your food is an example of one of these salts: It's sodium chloride, a compound of the metal sodium with chlorine. Hundreds of other kinds of salts exist in the world as well because metals are so willing to react with other elements. This is the main reason that metals are often difficult to extract from ores: They tend to react with oxygen in the air or sulfur in the ground.

• Metals and Their Properties: Physical and Chemical: This worksheet offers an easy-to-follow breakdown of the properties of metal.
• Chemical Properties: Check out pictures, descriptions, and formulas that explain the chemical reactions and changes that occur in metal.