Where is caesium found

That all began to change with the world's first railways, here in the UK. Then the fact that midday in London was 10 minutes before midday in Bristol - because that was how long it took the sun to figuratively sail west across the sky - became an issue, and a very serious one. It wasn't just that passengers would miss their trains. Inconsistencies in timekeeping were causing an increasing number of near misses and even train crashes.

It imposed London time across the whole network, the first occasion time was synchronised between different locations to a single standard. The move was very controversial. Suddenly, your time of day was to be dictated by the Royal Observatory in faraway Greenwich. The Dean of Exeter stoutly refused to adjust the Exeter Cathedral clock to meet the demands of the railway company.

In Bristol a compromise was found: two minute hands, one showing local time, the other Railway Time. Nevertheless Railway Time gradually became the standard across Britain, and the same happened around the world wherever railways were built.

But what does all this have to do with caesium, you are probably asking yourself? The answer is that whenever you have a network operating over distance, accurate timekeeping is essential for synchronisation.

And the faster the speed of travel, the more accurate the timekeeping must be. Hence in the modern world, where information travels at almost the speed of light down wires or through the air, accuracy is more important than ever.

What caesium has done is to raise the standards for the measurement of time exponentially. I took a trip to the home of accurate timekeeping in Britain. The series of off-the-peg glass office buildings located on an upmarket industrial park belie the exotic endeavours that take place within. The NPL is one of the world's leading centres for research into the measurement of time and is where the British standards for the seven key scientific units of measurement are kept.

It was here in the s that the physicist Louis Essen developed the first quartz ring clock, the most accurate timepiece of its day, and a precursor of the caesium clock. Quartz clocks exploit the fact that quartz crystals vibrate at a very high frequency if the right electrical charge is applied to them.

This is known as a resonant frequency, everything on earth has one. It is hitting the resonant frequency of a champagne glass that - allegedly - allows a soprano to shatter it when she hits her top note. It also explains why a suspension bridge at Broughton in Lancashire collapsed in Troops marching over it inadvertently hit its "resonant frequency", setting up such a strong vibration the bolts sheared.

Ever since, troops have been warned to "break step" when crossing suspension bridges. To understand how this phenomenon helps you to measure time, think of the pendulum of a grandfather clock. The clock mechanism counts a second each time it swings. Quartz plays the same role as a pendulum, just a lot quicker: it vibrates at a resonant frequency many thousands of times a second. And that's where caesium comes in. It has a far higher resonant frequency even than quartz - 9,,, Hz, to be precise.

This is one reason Essen used the element to make the first of the next generation of clocks - the "atomic" clocks. Essen's quartz creation erred just one second in three years. His first atomic clock created at NPL in was accurate to one second in 1. He opens it up and pulls out a wad of fabric padding. Wrapped inside is a sealed glass ampoule full of a silvery-gold metal.

He warms the ampoule in his hand. The metal gradually melts into liquid. He explains that the careful packaging is necessary because caesium is an alkali metal, from the first column of the periodic table. As such, it is very reactive, even more so than sodium or potassium. Being in column one means that caesium has a single electron in its outer shell.

That is what makes it so chemically reactive, and it was also the behaviour of this electron that Essen was interested in. Source: Encyclopaedia Britannica. I'm led to a room deep inside the NPL complex protected by a state-of-the-art electronic lock. This is where they keep the machine that sets the standard for the measurement of time in Britain. It is known as the "caesium fountain" and inside the room I meet the keeper of the fountain, Krzysztof Szymaniec.

Don't imagine the sort of fountain that plays in the gardens of a palace, this looks like a domestic hot water tank made of stainless steel with all sorts of extra wires and other gubbins attached at the bottom.

It may not be pretty, but it is one of the most accurate clocks on earth. Szymaniec explains it works by using a series of lasers to push a group of caesium atoms so tightly together that they almost stop vibrating, dropping their temperature to a smidgen above absolute zero.

Other lasers launch this atomic "molasses" up into the tank bit of the machine. The atoms fall back under gravity - hence "fountain". What the machine does next is tune a beam of microwave radiation into the resonant frequency of the caesium. Just like champagne glasses and bridges, when you hit the right frequency the caesium gets excited, and what happens is that outermost electron jumps into a wider orbit. Say what?

Cesium is pronounced as SEE-zee-em. Cesium was discovered by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, German chemists, in through the spectroscopic analysis of Durkheim mineral water. They named cesium after the blue lines they observed in its spectrum. Today, cesium is primarily obtained from the mineral pollucite CsAlSi 2 O 6. Obtaining pure cesium is difficult since cesium ores are frequently contaminated with rubidium , an element that is chemically similar to cesium.

Metallic cesium is too reactive to easily handle and is usually sold in the form of cesium azide CsN 3. Cesium reacts with cold water to form hydrogen gas and a solution of cesium ions and hydroxide ions.

The reaction is so explosive that it often shatters the container. The sublimation energy 1 is the smallest of the alkali metals because the Cs atoms are the biggest.

Cesium is an especially dangerous fission product because of its high yield during fission, moderate half-life, high-energy decay pathway, and chemical reactivity. Because of these properties, cesium is a major contributor to the total radiation released during nuclear accidents. Cesium is more reactive. Despite the fact that reactivity increases as we go down group 1 or Alkali metals , as the outermost electrons get further and further away from the nucleus and as a result, become easier to remove from the atom.

Hence as a result we see that cesium is more reactive than francium. Nowadays, Cesium is used as the definition for the second due to the reliable frequency of microwave it emits. The definition is: The second is the duration of 9,,, periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium atom.

Physical properties Cesium is a silvery-white, shiny metal that is very soft and ductile. Ductile means capable of being drawn into thin wires.

Its melting point is It melts easily in the heat of one's hand, but should never be handled that way! Robert Bunsen Gustav Kirchhoff. The atomic masses of these isotopes range from to Only one isotope, Cs , is stable. The longest-lived radioisotopes are Cs with a half-life of 2. Alkali metals are highly reactive , have one electron in their outer shell, and do not occur freely in nature, according to ChemicalElements. Cesium is highly reactive and combines readily with other elements, especially oxygen and other gases, and nonmetals, according to Encyclopedia Britannica.

Metal Alkali metal Period 6 element. Where is Caesium found? Category: science chemistry. Source: Cesium is found in the minerals pollucite and lepidolite.

Commercially, most cesium is produced as a byproduct of the production of lithium metal.