Strontium

Strontium is a chemical element with the symbol Sr and atomic number 38. It is a soft, silver-white yellowish metallic element that is very chemically reactive. When strontium touches air, it gets a dark layer on its surface.

Strontium is found in nature in two minerals: celestine and strontianite. People mine these minerals to get the element. Both strontium and strontianite are named after the village of Strontian in Scotland, where the mineral was first found in 1790 by Adair Crawford and William Cruickshank. It was recognized as a new element because it gives a special red color in a flame test.

In 1808, the element was first made as a metal by Humphry Davy using a process called electrolysis. In the 1800s, strontium was used to help make sugar from sugar beets. Later, it was important for making the glass screens of old television cathode-ray tubes. Today, as televisions have changed, we use strontium less.

Natural strontium, mostly made of the isotope strontium-88, is safe in small amounts. But a man-made form called strontium-90 is radioactive and can be dangerous. It is found in nuclear fallout, because the body treats it like calcium.

Characteristics

Strontium is a soft, silvery metal with a pale yellow color. It is very reactive, like the metals calcium and barium. It melts at 777 °C and boils at 1377 °C.

Strontium reacts with water to make strontium hydroxide and hydrogen gas. It also burns in air to form strontium oxide and strontium nitride. When you cut it, it turns yellow quickly as it reacts with air. Strontium is often stored in oil to stop it from reacting.

Isotopes

Main article: Isotopes of strontium

Natural strontium is a mix of four stable isotopes: ⁸⁴Sr, ⁸⁶Sr, ⁸⁷Sr, and ⁸⁸Sr. The most common is ⁸⁸Sr, making up about 82.6% of all natural strontium. Some isotopes of strontium are used in medicine.

History

Strontium is named after the village of Strontian in Scotland, where it was first found in old mines.

In 1790, scientists found that minerals from Strontian acted differently from other minerals. They called these minerals strontianite because they were special. Later, in 1808, a scientist named Sir Humphry Davy was the first to separate the element strontium.

For many years, strontium was used to help make sugar from sugar beets in factories. It was important until new methods came along. During tests of nuclear weapons, scientists discovered a form of strontium called strontium-90. They studied it because it acts like calcium in the body.

Occurrence

See also: Category:Strontium minerals

Strontium is found in nature quite often. It is the 15th most common element on Earth. We find it mainly in two minerals: celestine (SrSO₄) and strontianite (SrCO₃). Celestine is more common to mine, but strontianite is more useful in products.

In water, strontium acts a bit like calcium. It mixes with other minerals and sticks to soil particles. In the ocean, strontium is found at a level of about 8 mg/L.

Production

Strontium comes from a mineral called celestine. Spain and Iran are the main producers, with China and Mexico also making a lot.

To make strontium, celestine is turned into a compound called carbonate. This can be done with a special liquid or by heating it with coal. The result is a dark material that is dissolved in water. Adding a gas creates strontium carbonate.

The metal form of strontium is made by heating strontium oxide with aluminium. It can also be made in smaller amounts using electrolysis.

Strontium is important in the European Union, and most of it comes from Spain.

Applications

The main use of strontium was in making glass for old colour televisions. It helped stop harmful invisible rays from escaping. But now, as we use new types of screens, this use has gone down.

Because strontium acts like calcium in our bodies, scientists can study it in old bones to learn where people lived long ago. This helps us understand how ancient people moved and lived.

Strontium also makes fireworks glow a bright red and is used in some glow-in-the-dark toys. It can even help people with sensitive teeth when added to special toothpaste.

Radioactive strontium

Some forms of strontium can give off helpful energy for treating pain caused by certain types of cancer. Another form can provide power for special scientific tools, though it needs careful handling because of the energy it releases.

Biological role

Acantharea, a group of tiny sea creatures, build skeletons using strontium sulfate. In living things, strontium can act a bit like calcium. Most of the strontium we take in ends up in our bones, though there is only a tiny amount compared to calcium.

The human body treats strontium almost like calcium. Stable forms of strontium can be a health concern because we usually take in about two milligrams of it each day. Strontium acts like calcium and collects in our bones. In adults, it mainly sticks to the outside of bones. In children, whose bones are still growing, strontium might help build strong bones. Over time, strontium can leave bones and move through the bloodstream.

There is a medicine called strontium ranelate that helps bones grow stronger. However, it can also increase the risk of blood clots and heart problems, so its use is now limited. Some supplements still contain strontium, but there isn’t much research on its safety. People with a history of blood clotting issues should avoid it.

When put on the skin, strontium can help reduce irritation and speed up healing.

Nuclear waste

Strontium-90 is a special material made in nuclear reactors used for nuclear power. It is part of the tricky waste from these reactors. It takes about 29 years for half of it to change and become less harmful, but it can still take a long time to become safe. If people drink water or eat food with this material, it might cause health problems.

Scientists are looking for ways to clean up this material. Some tiny water plants, called algae, can pick out strontium from water. This could help treat water from nuclear sites. Studies with different types of algae suggest these tiny plants might be useful for cleaning up radioactive wastewater.