What is the difference between caesium and cesium

In air the levels of cesium are generally low, but radioactive cesium has been detected at some level in surface water and in many types of foods. The amount of cesium in foods and drinks depends upon the emission of radioactive cesium through nuclear power plants, mainly through accidents.

These accidents have not occurred since the Chernobyl disaster in People that work in the nuclear power industry may be exposed to higher levels of cesium, but many precautionary measurements can be taken to prevent this. It is not very likely that people experience health effects that can be related to cesium itself.

When contact with radioactive cesium occurs, which is highly unlikely, a person can experience cell damage due to radiation of the cesium particles. Due to this, effects such as nausea, vomiting, diarrhoea and bleeding may occur.

When the exposure lasts a long time people may even lose consciousness. Coma or even death may than follow. How serious the effects are depends upon the resistance of individual persons and the duration of exposure and the concentration a person is exposed to. Cesium occurs naturally in the environment mainly from erosion and weathering of rocks and minerals. It is also released into the air, water and soil through mining and milling of ores.

Radioactive isotopes of cesium may be released into the air by nuclear power plants and during nuclear accidents and nuclear weapons testing. The radioactive isotopes can only be decreased in concentration through radioactive decay.

Non-radioactive cesium can either be destroyed when it enters the environment or react with other compounds into very specific molecules. Both radioactive and stable cesium act the same way within the bodies of humans and animals chemically. Cesium in air can travel long distances before settling on earth. Atomic radius, non-bonded Half of the distance between two unbonded atoms of the same element when the electrostatic forces are balanced. These values were determined using several different methods.

Covalent radius Half of the distance between two atoms within a single covalent bond. Values are given for typical oxidation number and coordination. Electron affinity The energy released when an electron is added to the neutral atom and a negative ion is formed. Electronegativity Pauling scale The tendency of an atom to attract electrons towards itself, expressed on a relative scale. First ionisation energy The minimum energy required to remove an electron from a neutral atom in its ground state.

The oxidation state of an atom is a measure of the degree of oxidation of an atom. It is defined as being the charge that an atom would have if all bonds were ionic. Uncombined elements have an oxidation state of 0. The sum of the oxidation states within a compound or ion must equal the overall charge.

Data for this section been provided by the British Geological Survey. An integrated supply risk index from 1 very low risk to 10 very high risk. This is calculated by combining the scores for crustal abundance, reserve distribution, production concentration, substitutability, recycling rate and political stability scores. The percentage of a commodity which is recycled. A higher recycling rate may reduce risk to supply. The availability of suitable substitutes for a given commodity. The percentage of an element produced in the top producing country.

The higher the value, the larger risk there is to supply. The percentage of the world reserves located in the country with the largest reserves.

A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators. A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators.

Specific heat capacity is the amount of energy needed to change the temperature of a kilogram of a substance by 1 K. A measure of the stiffness of a substance. It provides a measure of how difficult it is to extend a material, with a value given by the ratio of tensile strength to tensile strain. A measure of how difficult it is to deform a material. It is given by the ratio of the shear stress to the shear strain.

A measure of how difficult it is to compress a substance. It is given by the ratio of the pressure on a body to the fractional decrease in volume. A measure of the propensity of a substance to evaporate.

It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system. This Site has been carefully prepared for your visit, and we ask you to honour and agree to the following terms and conditions when using this Site. Copyright of and ownership in the Images reside with Murray Robertson. The RSC has been granted the sole and exclusive right and licence to produce, publish and further license the Images. The RSC maintains this Site for your information, education, communication, and personal entertainment.

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Glossary Allotropes Some elements exist in several different structural forms, called allotropes. Discovery date Discovered by Gustav Kirchhoff and Robert Bunsen Origin of the name The name comes from the Latin 'caesius', meaning sky blue, and derived from its flame colour. Glossary Group A vertical column in the periodic table.

Fact box. Group 1 Melting point Glossary Image explanation Murray Robertson is the artist behind the images which make up Visual Elements. Appearance The description of the element in its natural form. Biological role The role of the element in humans, animals and plants. Natural abundance Where the element is most commonly found in nature, and how it is sourced commercially.

Uses and properties. Image explanation. The symbol reflects the use of the element in highly accurate atomic clocks. Caesium is a soft, gold-coloured metal that is quickly attacked by air and reacts explosively in water. The most common use for caesium compounds is as a drilling fluid. They are also used to make special optical glass, as a catalyst promoter, in vacuum tubes and in radiation monitoring equipment. These clocks are a vital part of the internetand mobile phone networks, as well as Global Positioning System GPS satellites.

They give the standard measure of time: the electron resonance frequency of the caesium atom is 9,,, cycles per second. Some caesium clocks are accurate to 1 second in 15 million years. Biological role. Caesium has no known biological role. Caesium compounds, such as caesium chloride, are low hazard. Natural abundance. Caesium is found in the minerals pollucite and lepidolite. Pollucite is found in great quantities at Bernic Lake,Manitoba, Canada and in the USA, and from this source the element can be prepared.

However, most commercialproduction is as a by-product of lithium production. Help text not available for this section currently. Elements and Periodic Table History. Caesium was almost discovered by Carl Plattner in when he investigated the mineral pollucite caesium aluminium silicate. It was later realised that he mistook the caesium for sodium and potassium. They examined mineral water from Durkheim and observed lines in the spectrum which they did not recognise, and that meant a new element was present.

They produced around 7 grams of caesium chloride from this source, but were unable to produce a sample of the new metal itself. Atomic data. Glossary Common oxidation states The oxidation state of an atom is a measure of the degree of oxidation of an atom. Oxidation states and isotopes.

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. This is known as a "transition". As the electron moves out into the wider orbit it absorbs energy, and as it jumps back in it releases it in the form of light, fluorescing very slightly.

That means you can tell when you've hit the sweet spot of 9,,, Hz. It's because this transition frequency is so much higher than the resonant frequency of quartz that a caesium clock is so much more accurate. The caesium fountain at NPL, Szymaniec tells me proudly, is accurate to one second in every million years.

That means it would only be a second out if it had started keeping time back in the peak of the Jurassic Period when diplodocus were lumbering around and pterodactyls wheeling in the sky. But modern technology means these days even more staggeringly accurate clocks are possible.

That's because caesium was always a compromise element when it came to timekeeping. Louis Essen chose caesium, explains Szymaniec, because the frequency of its transition was at the limit of what the technology of his day could measure. At NPL they are experimenting with the elements strontium and ytterbium that operate at far, far higher frequencies - right up in the optical rather than the microwave spectrum.

The frequency of the transition of strontium, for example, is ,,,, A strontium clock developed in the US would only have lost a second since the earth began: it is accurate to a second in five billion years.