Plutonium

This is a special metal.

It looks like shiny silver at first. Soon, it turns a dull gray.

This metal can feel warm. It makes heat all by itself. This heat helps power ships in space.

The metal is also very dangerous. It can get inside your bones. People must be very careful with it. It was named after the planet Pluto. It is a very rare metal.

Plutonium is a silvery-gray metal.

It looks shiny like nickel at first. However, it turns dull when it touches air.

This metal is radioactive. This means it gives off power through decay. This process makes the metal feel warm to the touch. Some people say it feels like a warm rabbit.

This heat can power spacecraft.

Scientists first made plutonium in 1940 and 1941. They used a machine called a cyclotron. They named it after the planet Pluto.

Most plutonium is made in special reactors. Some is found in nature in tiny amounts.

Plutonium has many forms called allotropes. These are different ways the atoms can be arranged. Some forms are hard and brittle like iron. Other forms are soft and easy to shape. This makes the metal hard to work with. Some types of plutonium are fissile. This means they can sustain a nuclear chain reaction. This makes them useful for nuclear reactors and weapons.

Handling this metal is very dangerous. It can build up in human bones.

Plutonium is a unique chemical element with the symbol Pu and atomic number 94.

It is a silvery-gray metal that looks bright like nickel when it is first seen. However, it quickly tarnishes when it touches air to form a dull coating.

This metal is radioactive, which means it naturally gives off energy. This energy can make a piece of plutonium feel warm to the touch. One person even said it feels warm like a live rabbit.

Because it is radioactive, handling it is very dangerous for people. It can build up inside human bones if it gets into the body.

This metal has many different forms called allotropes. An allotrope is a way that the atoms inside the metal are arranged.

Plutonium has six of these forms at normal pressure. Some forms are hard and brittle like gray cast iron. Other forms can be made soft and easy to shape by mixing them with metals like gallium. This makes the metal very hard to work with because it changes state so easily. If it touches moist air, it can even expand by up to 70% in size. This expansion can cause the metal to flake off into a powder that can catch fire easily.

Scientists first made plutonium in late 1940 and early 1941.

A team at the University of California, Berkeley, used a machine called a cyclotron to create it. They did this by hitting uranium-238 with particles called deuterons. This process first created neptunium-238, which then decayed into plutonium. They named the new element after the planet Pluto. At that time, Pluto was still considered a planet. Because of wartime secrecy, the team could not publish their discovery until 1948.

There are many different versions of plutonium called isotopes.

Some isotopes, like plutonium-239 and plutonium-241, are fissile. This means they can sustain a nuclear chain reaction. This ability makes them useful for nuclear reactors and weapons.

Other versions, like plutonium-238, are used to create heat. This heat can power spacecraft using special generators.

Scientists grade plutonium based on how much plutonium-240 it contains. Weapons-grade plutonium has less than 7% of this isotope. Fuel-grade has between 7% and 19%, and reactor-grade has more than 19%.

Plutonium is a very important part of how we understand energy. While most plutonium is made in special reactors, tiny amounts can be found in nature. These small amounts appear in uranium deposits when uranium atoms capture neutrons.

Some heavy versions of the element might have existed since the Earth was first formed. However, we have not yet built tools sensitive enough to find them. Today, managing plutonium waste is a big job for the environment. It is a metal that connects the tiny world of atoms to the huge world of space travel.

Plutonium is a heavy, silvery-gray chemical element with the symbol Pu and atomic number 94.

It belongs to a group of elements called actinides. While it looks bright like nickel when first exposed, it oxidizes very quickly in the air. This process creates a dull gray, yellow, or olive green coating.

Plutonium is also highly radioactive, meaning its atoms naturally release energy. This energy can make a piece of the metal feel warm to the touch. Because it can accumulate in human bones, handling the element is extremely dangerous.

One of the most unusual things about plutonium is its many allotropes. An allotrope is a different structural form of the same element.

At room temperature, plutonium usually exists in its alpha (α) form. This form is hard and brittle, similar to gray cast iron. However, the metal is very sensitive to changes in temperature and pressure. It has six common allotropes at normal pressure, and even a seventh called zeta (ζ) at high temperatures. These forms have very different densities, ranging from 16.00 g/cm³ to 19.86 g/cm³. This makes machining the metal very difficult because it changes state so easily. To make it easier to work with, scientists often alloy it with metals like gallium. This stabilizes the delta (δ) form, which is soft and malleable like aluminum.

Plutonium is also chemically very reactive. It reacts with several substances, including carbon, halogens, nitrogen, silicon, and hydrogen. If the metal is exposed to moist air, it forms oxides and hydrides. This chemical reaction can cause the metal to expand by up to 70% in volume. As it expands, the surface can flake off into a fine powder. This powder is pyrophoric, which means it can catch fire spontaneously.

Scientists first discovered plutonium through a complex process of synthesis. In late 1940 and early 1941, a team at the University of California, Berkeley, used a cyclotron to create it. They bombarded uranium-238 with deuterons to produce neptunium-238. This neptunium then underwent beta decay to become plutonium-238. The team named the element after the planet Pluto, following the naming patterns of uranium and neptunium. Because of the secrecy of World War II, they could not publish their findings until 1948.

There are many different isotopes, or versions, of plutonium.

Some isotopes are fissile, such as plutonium-239 and plutonium-241. Fissile means the nucleus can split when struck by a slow neutron, sustaining a nuclear chain reaction. This process releases massive amounts of energy. For example, fissioning just one kilogram of plutonium-239 produces an explosion equivalent to 17 kilotons of TNT.

Other isotopes, like plutonium-238, are not fissile but emit alpha particles. These particles release heat, which is useful for powering spacecraft through radioisotope thermoelectric generators.

The quality of plutonium is determined by its isotopic composition. Scientists categorize it into different grades based on the percentage of plutonium-240 it contains. Plutonium-240 has a high rate of spontaneous fission, which increases the neutron flux. This high neutron level can cause a weapon to detonate too early. Weapons-grade plutonium contains less than 7% plutonium-240. Fuel-grade contains between 7% and 19%, and reactor-grade contains 19% or more. Supergrade plutonium contains less than 4% and is used in specific Navy weapons.

While most plutonium is manufactured in specialized reactors, it can occur naturally in tiny amounts. In uranium deposits, uranium-238 can capture neutrons to create trace amounts of plutonium. Some scientists believe that heavy isotopes like plutonium-244 might have existed since the Earth was formed. However, current experiments are not yet sensitive enough to detect these primordial traces. Today, the management of plutonium waste from power plants and dismantled weapons is a major environmental and safety concern.