Rubidium

Rubidium is a chemical element with the symbol Rb and atomic number 37. It belongs to the alkali metal group, similar to potassium and caesium, and is a very soft, whitish-grey solid. Rubidium is special because it is the first alkali metal that is denser than water.

German chemists Robert Bunsen and Gustav Kirchhoff discovered rubidium in 1861 using a technique called flame spectroscopy. The name rubidium comes from the Latin word rubidus, meaning deep red, because of the color it shows in its emission spectrum.

Rubidium has many uses in chemistry and electronics. Because it vaporizes easily and has a good range for laser absorption, it is often used in experiments that manipulate atoms with lasers. Although rubidium is not a nutrient that living organisms need, its ions behave similarly to potassium ions and are taken up by animal cells in much the same way.

Characteristics

Rubidium is a very soft, silvery-white metal. It melts at a low temperature of 39.3 °C (102.7 °F) and boils at 688 °C (1,270 °F). It can mix with mercury to form special mixtures and also combines with several other metals.

Rubidium reacts very strongly with water, creating rubidium hydroxide and hydrogen gas. This reaction can be very intense and may even cause sparks or small explosions. Rubidium can also catch fire when exposed to air on its own.

Rubidium chloride is one of the most used rubidium compounds. It helps scientists study how living cells take in DNA. Other common compounds include rubidium hydroxide, rubidium carbonate used in special glass, and rubidium silver iodide, which is great for use in thin film batteries.

Rubidium has two main types, called isotopes: stable ⁸⁵Rb and radioactive ⁸⁷Rb. The radioactive type has been used to find the age of rocks. There are also other rubidium isotopes made in labs, but they break down quickly.

Occurrence

Rubidium is not very common. It makes up about 0.05% of the Earth's crust and is the 23rd most common element there. You can find it in minerals like leucite, pollucite, carnallite, and zinnwaldite. Another mineral, lepidolite, contains between 0.3% and 3.5% rubidium and is often used to get the element.

Seawater has an average of 125 micrograms of rubidium per liter. This is much less than the amount of potassium in seawater but more than the amount of caesium.

Because of its size, rubidium stays in liquid magma as it cools and solidifies. This means it can be found in special types of rock called zone pegmatite ore bodies. These rocks can contain rubidium along with other elements like caesium.

Two important places to find rubidium are at Bernic Lake in Manitoba, Canada, and on the Italian island of Elba. Both of these places also contain other useful elements.

Production

Rubidium is found in Earth's crust, but there isn't much use for it, so only a small amount — about 2 to 4 tonnes each year — is made. There are a few ways to separate rubidium from other elements like potassium and caesium. One way is to use a process called fractional crystallization, which takes many steps to get pure rubidium. Other methods include the chlorostannate process and the ferrocyanide process.

In the 1950s and 1960s, a by-product from making potassium called Alkarb was a main source of rubidium. Today, rubidium is often made as a by-product when companies produce caesium from a mineral called pollucite.

History

Rubidium was discovered in 1861 by Robert Bunsen and Gustav Kirchhoff in Heidelberg, Germany. They found it in a mineral called lepidolite by using a special tool called a spectroscope. They named it rubidium after the bright red color they saw, which comes from the Latin word rubidus, meaning "deep red".

Bunsen and Kirchhoff worked hard to separate rubidium from other materials. They used a process called fractional crystallization to get rubidium in a form they could study. Later, they made a tiny amount of rubidium metal, which was very reactive. Rubidium didn’t have many uses until the 1920s, but today it is important for research, especially in chemistry and electronics. In 1995, a special form of rubidium helped scientists create something called a Bose-Einstein condensate, for which they received a Nobel Prize in 2001.

Applications

Rubidium has been studied for use in special generators that use magnetic fields to produce electricity. It is also commonly used in scientific tools for cooling atoms and studying their behavior. This is possible because rubidium can be easily vaporized and works well with lasers.

Rubidium is important in very accurate clocks and timing devices used in communication equipment. It can also be used in certain types of glass, in studying biological processes, and in medical imaging to help find and see brain tumors. Additionally, rubidium has been explored for potential benefits in treating certain mood conditions.

Precautions and biological effects

Rubidium can react very strongly with water and may cause fires, so it is usually stored safely under dry mineral oil or sealed in glass containers. Even a little bit of air can cause rubidium to form peroxides, so it needs to be stored carefully, much like potassium.

When dissolved in water, rubidium behaves similarly to potassium and is found mostly inside our cells. It is not very harmful; the human body naturally contains a small amount of rubidium, and even increasing this amount significantly did not cause problems in tests. The body gets rid of rubidium over about a month. However, if too much rubidium replaces potassium in muscles, it can be dangerous.