Molten iron, a metal, flows into a casting mold. Iron turns liquid at around 1,500º Celsius (2,750º Fahrenheit).

Jill King/EyeEm/iStock/Getty Images Plus

A towering skyscraper bends under a strong gust of wind, but it doesn’t snap. That’s one advantage metals can offer. Being malleable (MAAL-ee-ah-bul), metals can be hammered into sheets without shattering. Because they’re ductile (DUK-tul), they can be easily pulled and stretched into wires without snapping. Metals also can conduct electricity. 

But not all metals are equally prized. Although more than three-fourths of the 118 elements on the periodic table are metals, we craft tools from only a few of these. That’s because familiar metals, such as iron and silver, are special. For one thing, they’re easier to find than other metals. (Although most known elements are metals, they are fairly uncommon in nature.) 

Familiar metals also are less reactive than most other metals. Reactivity refers to how easily a substance reacts chemically with other substances. Low-reactivity metals are safer to handle than high-reactivity ones. Pure silver is so safe that we use it for jewelry and flatware. But pure sodium, also a metal, is so reactive it explodes on contact with water!

Good thing, then, that pure sodium never occurs naturally. Instead, we find it after it has already bonded chemically with one or more other elements. Sodium chloride, or table salt, is a common example. And that highlights another reason low-reactivity metals are so useful. They often occur naturally in forms easy to work with. For example, silver can be mined as pure silver. But if we wanted pure sodium, we’d need a way to separate it from one of the chemicals to which it had bonded. That can be hard to do.

Sometimes, a special project — such as the $10-billion James Webb Space Telescope — may call for a fairly rare metal. After 25 years in development, the telescope launched on Christmas morning in 2021. For this eye in the sky, NASA chose the rare metal beryllium (Beh-RIL-ee-um) to make its honeycomb of gold-plated mirrors. Beryllium is super lightweight. That makes it easy to launch into space. Beryllium also holds its shape in frigid temperatures. When rocketed from Earth’s relatively lukewarm air to the cryogenic (super-cold) temperatures of space, metals contract and bend. Since telescopes work by reflecting light, any tiny change in their shape could ruin a telescope’s images. But beryllium remains more stable than most metals during such sharp temperature changes.

If it’s able, an atom will steal electrons from a neighboring atom. It won’t steal all of them, but just enough to be stable. Different elements have different numbers of electrons that — at least in theory — can be stolen by a neighbor. These are called valence (VAY-lents) electrons. They are the outer, orbiting electrons that can become part of chemical bonds.

Metal atoms differ from nonmetal ones in how well they steal valence electrons from other atoms. One might say that metals are bad thieves. Instead of capturing a neighbor’s electrons, they usually give up their own. This tendency to lose electrons is described as their “metallic character.”

Nonmetallic elements, therefore, have a low metallic character. Among these nonmetals are carbon, oxygen and nitrogen. When it comes to electron thieves, nonmetals are the best. King of those nonmetals is fluorine. When it comes to electron-stealing, fluorine’s a downright bully. So it’s highly reactive. 

Metals do desire electrons, but only weakly. In many ways, however, this weakness turns out to be metals’ strength.  Their malleability (bendiness), ductility (stretchiness) and conductivity come from the tendency of these elements to lose electrons.

Most chemical bonds occur as atoms fight over electrons. A metallic bond occurs when two metal atoms bond. Neither of them seems to care much which atom ends up with the extra electrons.

Contrast this with an ionic bond. That occurs when a metal (like sodium) bonds with a nonmetal (such as chlorine). Due to big differences in their metallic character, the nonmetal steals electrons from the metal atom and keeps those electrons. 

Chemical bonding occurs after the theft. The metal and nonmetal remain stuck together because they now have opposite charges. Both atoms started with a neutral charge. Once the nonmetal gained an electron, it became negative. (That’s because electrons have a negative charge.) But the metal lost an electron. That left the metal with an overall positive charge. Notice that the metal isn’t positive because it gained a positive charge. It’s positive because it lost a negative one. These oppositely charged atoms, now called ions, attract each other and stick together.

Metal bonds also differ from the covalent bonds that form when two nonmetals join up. There, both nonmetals try to wrestle electrons from the other. But since both have strong claims on the other’s electrons, they both fail. The nonmetals end up locked in a perpetual tug-of-war. Because neither atom “wins,” these atoms are described as “sharing” their electrons. 

But when two metal atoms bump into each other, they don’t fight for electrons. Neither really wants the electrons badly enough. When many metal atoms end up stuck together, as in a piece of metal, their electrons move from one atom to another to another to another. Scientists describe these electrons as “delocalized.”

Delocalized electrons explain why metals conduct electricity. After all, electricity is just the movement of electrons. One model used to explain metallic bonds envisions metal atoms as though they float through an ocean of electrons.

Delocalized electrons don’t just explain metals’ conductivity. They also explain metals’ malleability and ductility.Metallic bonds allow metal atoms to move around within their electron sea, yet still remain bonded. That would never be possible if they were locked rigidly together with covalent or ionic bonds.

The atoms in some metals move around more easily than others. Metals with easily moveable atoms are too malleable to use in tool-making. They’re too soft. Sodium metal is one such example. Sodium is malleable enough to cut with a spatula. Most of our really useful metals, especially those used for making tools, are hard enough to keep their shape. Take iron, for instance. To forge an iron sword, a blacksmith must reposition bajillions of iron atoms. And that’s no easy task.

So, then, how do blacksmiths do it? Keep in mind that atoms never sit still. They move and shake. And hot atoms shake more than cold ones, giving hot atoms more freedom. In molten metal, the bonds between atoms weaken a lot. So a blacksmith will boost a forge’s heat to upwards of 1,600º Celsius (2,900º Fahrenheit). This intense fever weakens those metallic bonds, allowing the blacksmith to hammer the metal into shape.

Once the new sword cools, its atoms slow and the metallic bonds re-secure. 

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Jewelry almost never contains pure gold. It would simply be too soft. So metal-workers mix gold with other metals, often copper, to make it less malleable. Such mixed metals are called alloys. Alloys can also be metals mixed with a tiny dash of some nonmetal.

Carbon steel is an iron alloy made with a pinch of carbon. Skyscrapers and bridges are made from lots of carbon steel. So are many kitchen knives and screwdrivers. The carbon in carbon steel reinforces the iron, making it harder. But increasing a metal’s hardness also drops its malleability.

In fact, too much carbon will make steel brittle. And as metals get cold, this problem only worsens. In April 1912, the cruise ship Titanic struck an iceberg on its maiden voyage and sank. More than 1,500 people died. Studies on the ship’s gashed hull suggest that the Titanic‘s steel became brittle in the Atlantic’s frigid waters. The Titanic’s steel alloy became brittle at 32 ºC (90 ºF). The night Titanic sank, the water was just –2 ºC (28 ºF). 

Engineers today would use a different steel. For example, a modern steel-type called ASTM A36 can handle –27 ºC (–17 ºF) before becoming as brittle as the Titanic‘s had. The difference is in the alloy. The Titanic‘s steel “had a lot more sulfur content and a lot less manganese,” explains Andrew Falkowski. He’s a materials engineer in Salt Lake City, Utah. He also co-hosts the Materialism Podcast, a show about materials science.

You can tell how metallic any element is just by finding it on the periodic table. Metallic character exists on a spectrum. Elements fall somewhere between the least metallic — fluorine — and the most metallic — cesium (or francium, if you include lab-made elements). So in terms of metallic character, cesium and fluorine are polar opposites. Fluorine is the most reactive nonmetal in existence. And cesium is the most reactive metal. If these two ever meet, they’ll burst into intense white fire.

Find these elements on a periodic table, and you’ll notice something. They’re on opposite sides. That’s no coincidence.

Nonmetals occupy the upper right of the classic periodic table, including the entire far-right column. There’s one exception. Hydrogen is the only nonmetal that is not grouped with the nonmetals. Hydrogen is weird, mainly because its atoms are so tiny.

Metals occupy everywhere except the upper right. As you move away from the nonmetals, metallic character increases. It increases as you move from right to left and also as you move down.

Similar types of metals group together on the periodic table. For example, the far-left column contains sodium and the other so-called alkali metals. All of these react violently with nonmetals. The elements that lie between metals and nonmetals are called metalloids or semi-metals. They have properties of both metals and nonmetals. Arsenic and silicon are examples. In the middle are what are known as transition metals. That’s where most familiar metals live, such as gold, silver and copper.  

alkali metal: Any of six elements (cesium, francium, lithium, potassium, rubidium or sodium) that are highly reactive with water, creating strong bases — or alkalis — that can neutralize acids.

atom: The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.

bond: (in chemistry) A semi-permanent attachment between atoms — or groups of atoms — in a molecule. It’s formed by an attractive force between the participating atoms. Once bonded, the atoms will work as a unit. To separate the component atoms, energy must be supplied to the molecule as heat or some other type of radiation.

carbon: A chemical element that is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules. (in climate studies)

cesium: A metallic chemical element with the atomic number 55. Among its many uses, cesium serves as the basis of today’s atomic clocks and is used in many photo-electric cells.

chemical: A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

chemical bonds: Attractive forces between atoms that are strong enough to make the linked elements function as a single unit. Some of the attractive forces are weak, some are very strong. All bonds appear to link atoms through a sharing of — or an attempt to share — electrons.

chemical reactivity: A term that refers to the ease with which a substance undergoes chemical reactions.

copper: A metallic chemical element in the same family as silver and gold. Because it is a good conductor of electricity, it is widely used in electronic devices.

crust: (in geology) Earth's outermost surface, usually made from dense, solid rock.

delocalized electrons: Electrons of an atom, molecule or metal that are not associated with a specific atom or a specific covalent bond. Instead, they roam freely. Delocalized electrons are characteristic of metallic bonds and often are described as a sea of electrons.

ductility: (adj. ductile)A characteristic of a substance (such as a metal) that allows it to be pulled into wires without breaking.

electricity: A flow of charge, usually from the movement of negatively charged particles, called electrons.

electron: A negatively charged particle, usually found orbiting the outer regions of an atom; also, the carrier of electricity within solids.

element: A building block of some larger structure. (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.

engineer: A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need. (v.) To perform these tasks, or the name for a person who performs such tasks.

fluorine: An element first discovered in 1886 by Henri Moissan. It takes its name from the Latin word meaning “to flow.” Very reactive, chemically, this element had little commercial use until World War II, when it was used to help make a nuclear-reactor fuel. Later, it was used as ingredients (fluorocarbons) in refrigerants and aerosol propellants. Most recently, it has found widespread use to make nonstick coatings for frying pans, plumbers’ tape, and waterproof clothing.

forge: (noun) A furnace or shop where metal is worked and turned into new materials. (verb) To shape metals under heat and/or pressure, or (colloquially) to form one element from another under the intense heat and pressure inside stars.

hydrogen: The lightest element in the universe. As a gas, it is colorless, odorless and highly flammable. It’s an integral part of many fuels, fats and chemicals that make up living tissues. It’s made of a single proton (which serves as its nucleus) orbited by a single electron.

ion: (adj. ionized) An atom or molecule with an electric charge due to the loss or gain of one or more electrons. An ionized gas, or plasma, is where all of the electrons have been separated from their parent atoms.

iron: A metallic element that is common within minerals in Earth’s crust and in its hot core. This metal also is found in cosmic dust and in many meteorites.

malleable: Something whose shape can be altered, usually by hammering or otherwise deforming with pressure. (in social science) Attitudes or behaviors that can be changed with social pressure or logic.

manganese: Chemical element with the atomic number 25. It’s a hard gray metal in the transition series. Manganese is an important component of special steels.

mass: A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.

metal: Something that conducts electricity well, tends to be shiny (reflective) and is malleable (meaning it can be reshaped with heat and not too much force or pressure).

metallic bond: A type of chemical bond that connects metal atoms together. Metals tend to donate electrons, so this bond is characterized by free, so-called delocalized electrons. Together, those subatomic particlesare often referred to as an electron “sea.”

metallic character: A term that describes the reactivity of metals due to their tendency to give up electrons in chemical reactions.  Elements with high metallic character lose electrons most easily. Of the naturally occurring elements, cesium has the highest metallic character. Fluorine has the lowest.

metalloids: Also known as semimetals. These elements share some properties with both metals and nonmetals. On the periodic table, they lie along the border between metals and nonmetals. Silicon and arsenic are examples.

model: A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes. Or an individual that is meant to display how something would work in or look on others.

molten: A word describing something that is melted, such as the liquid rock that makes up lava.

NASA: Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.

reactive: (in chemistry) The tendency of a substance to take part in a chemical process, known as a reaction, that leads to new chemicals or changes in existing chemicals.

salt: A compound made by combining an acid with a base (in a reaction that also creates water). The ocean contains many different salts — collectively called “sea salt.” Common table salt is a made of sodium and chlorine.

skyscraper: A very tall building.

sodium: A soft, silvery metallic element that will interact explosively when added to water. It is also a basic building block of table salt (a molecule of which consists of one atom of sodium and one atom of chlorine: NaCl). It is also found in sea salt.

spectrum: (plural: spectra) A range of related things that appear in some order. (in light and energy) The range of electromagnetic radiation types; they span from gamma rays to X rays, ultraviolet light, visible light, infrared energy, microwaves and radio waves.

sulfur: A chemical element with an atomic number of sixteen. Sulfur, one of the most common elements in the universe, is an essential element for life. Because sulfur and its compounds can store a lot of energy, it is present in fertilizers and many industrial chemicals.

theory: (in science) A description of some aspect of the natural world based on extensive observations, tests and reason. A theory can also be a way of organizing a broad body of knowledge that applies in a broad range of circumstances to explain what will happen. Unlike the common definition of theory, a theory in science is not just a hunch. Ideas or conclusions that are based on a theory — and not yet on firm data or observations — are referred to as theoretical. Scientists who use mathematics and/or existing data to project what might happen in new situations are known as theorists.

tool: An object that a person or other animal makes or obtains and then uses to carry out some purpose such as reaching food, defending itself or grooming.

transition: The boundary where one thing (paragraphs, ecosystems, life stage, state of matter) changes or converts into another.

transition metal:Also known as transition elements. These metals are found in the center of the periodic table. In comparison to other elements, their properties tend to be more unpredictable. This unpredictability is due to their valence electrons being located in an electron shell section known as the d block. Mercury is one example.

valence: (in chemistry and physics)The electrons of an atom that are involved in chemical bonding. Usually valence electrons are the outermost electrons (those orbiting farthest from the nucleus). 

Podcast:​ ​​Materialism: A Materials Science Podcast. What Really Sunk the Titanic?  June 18, 2021​. Book: N.J. Tro. Chemistry: A Molecular Approach, AP Edition. Pearson, 2014.

Journal: K. Felkins et al. The royal mail ship Titanic: Did a metallurgical failure cause a night to remember? JOM. Vol. 50, January 1998, p. 12. doi: 10.1007/s11837-998-0062-7.

Katie Grace Carpenter is a science writer and curriculum developer, with degrees in biology and biogeochemistry. She also writes science fiction and creates science videos. Katie lives in the U.S. but also spends time in Sweden with her husband, who’s a chef.

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