Periodic Table > Caesium
 

Terminology


Allotropes
Some elements exist in several different structural forms, these are called allotropes.


For more information on Murray Robertson’s image see Uses/Interesting Facts below.

 

Fact Box Terminology


Group
Elements appear in columns or ‘groups’ in the periodic table. Members of a group typically have similar properties and electron configurations in their outer shell.


Period
Elements are laid out into rows or ‘periods’ so that similar chemical behaviour is observed in columns.


Block
Elements are organised into blocks by the orbital type in which the outer electrons are found. These blocks are named for the characteristic spectra they produce: sharp, principal, diffuse, and fundamental.


Atomic Number
The number of protons in the nucleus.


Atomic Radius/non -bonded (Å)
based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties, for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron Configuration
The arrangements of electrons above the last (closed shell) noble gas.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.


Melting Point (oC)
The temperature at which the solid-liquid phase change occurs.


Melting Point (K)
The temperature at which the solid-liquid phase change occurs.


Melting Point (oF)
The temperature at which the solid-liquid phase change occurs.


Boiling Point (oC)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (K)
The temperature at which the liquid-gas phase change occurs.


Boiling Point (oF)
The temperature at which the liquid-gas phase change occurs.


Sublimation
Elements that do not possess a liquid phase at atmospheric pressure (1 atm) are described as going through a sublimation process.


Density (kgm-3)
Density is the weight of a substance that would fill 1 m3 (at 298 K unless otherwise stated).


Relative Atomic Mass
The mass of an atom relative to that of Carbon-12. This is approximately the sum of the number of protons and neutrons in the nucleus. Where more than one isotope exists the value given is the abundance weighted average.


Key Isotopes (% abundance)
An element must by definition have a fixed number of protons in its nucleus, and as such has a fixed atomic number, however variants of an element can exist with differing numbers of neutrons, and hence a different atomic masses (e.g. 12C has 6 protons and 6 neutrons and 13C has 6 protons and 7 neutrons).


CAS number
The Chemical Abstracts Service registry number is a unique identifier of a particular chemical, designed to prevent confusion arising from different languages and naming systems (where several isotopes exist, a value is presented for the most prevalent isotope).

Fact Box

 
Group Melting point 28.5 oC, 83.3 oF, 301.65 K 
Period Boiling point 671 oC, 1239.8 oF, 944.15 K 
Block Density (kg m-3) 1900 
Atomic number 55  Relative atomic mass 132.905  
State at room temperature Solid  Key isotopes 133Cs 
Electron configuration [Xe] 6s1  CAS number 7440-46-2 
ChemSpider ID 4510778 ChemSpider is a free chemical structure database
 

Interesting Facts terminology


Image Explanation

Murray Robertson is the artist behind the images which make up Visual Elements. This is where the artist explains his interpretation of the element and the science behind the picture.


Natural Abundance

Where this element is most commonly found in nature.


Biological Roles

The elements role within the body of humans, animals and plants. Also functionality in medical advancements both today and years ago.


Appearance

The description of the element in its natural form.

Uses / Interesting Facts

 
Image explanation
The symbol used here reflects the use of the element in highly accurate atomic clocks.
Appearance
A soft, gold-coloured metal that is quickly attacked by air and reacts explosively in water. It is used in industry as a catalyst promoter, to make special glass, and in radiation monitoring equipment. The ‘caesium clock’ (atomic clock) is the standard measure of time: the electron resonance frequency of the caesium atom is 9,192,631,770 cycles per second.
Uses
Caesium is little used. It has a great affinity for oxygen and so is used in electron tubes, and it is also used in photoelectric cells and as a catalyst. A more interesting application is its use in atomic clocks, which are accurate to 5 seconds in 300 years.
Biological role
Caesium has no known biological role. It is non-toxic.
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 commercial production is as a by-product of lithium production.
 
Atomic Data Terminology

Atomic radius/non -bonded (Å)
Based on Van der Waals forces (where several isotopes exist, a value is presented for the most prevalent isotope). These values were calculated using a multitude of methods including crystallographic data, gas kinetic collision cross sections, critical densities, liquid state properties,for more details please refer to the CRC Handbook of Chemistry and Physics.


Electron affinity (kJ mol-1)
The energy released when an additional electron is attached to the neutral atom and a negative ion is formed (where several isotopes exist, a value is presented for the most prevalent isotope). *


Electronegativity (Pauling scale)
The degree to which an atom attracts electrons towards itself, expressed on a relative scale as a function bond dissociation energies, Ed in eV. χA - χB =(eV)-1/2sqrt(Ed(AB)-[Ed(AA)+Ed(BB)]/2), with χH set as 2.2 (where several isotopes exist, a value is presented for the most prevalent isotope).


1st Ionisation energy (kJ mol-1)
The minimum energy required to remove an electron from a neutral atom in its ground state (where several isotopes exist, a value is presented for the most prevalent isotope).


Covalent radius (Å)
The size of the atom within a covalent bond, given for typical oxidation number and coordination (where several isotopes exist, a value is presented for the most prevalent isotope). ***

Atomic Data

 
Atomic radius, non-bonded (Å) 3.430 Covalent radius (Å) 2.38
Electron affinity (kJ mol-1) 45.541 Electronegativity
(Pauling scale)
0.790
Ionisation energies
(kJ mol-1)
 
1st
375.704
2nd
2234.352
3rd
-
4th
-
5th
-
6th
-
7th
-
8th
-
 

Mining/Sourcing Information

Data for this section of the data page has been provided by the British Geological Survey. To review the full report please click here or please look at their website here.


Key for numbers generated


Governance indicators

1 (low) = 0 to 2

2 (medium-low) = 3 to 4

3 (medium) = 5 to 6

4 (medium-high) = 7 to 8

5 (high) = 9


Reserve base distribution

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %

(Where data are unavailable an arbitrary score of 2 was allocated. For example, Be, As, Na, S, In, Cl, Ca and Ge are allocated a score of 2 since reserve base information is unavailable. Reserve base data are also unavailable for coal; however, reserve data for 2008 are available from the Energy Information Administration (EIA).)


Production Concentration

1 (low) = 0 to 30 %

2 (medium-low) = 30 to 45 %

3 (medium) = 45 to 60 %

4 (medium-high) = 60 to 75 %

5 (high) = 75 %


Crustal Abundance

1 (low) = 100 to 1000 ppm

2 (medium-low) =10 to 100 ppm

3 (medium) = 1 to 10 ppm

4 (medium-high) = 0.1 to 1 ppm

5 (high) = 0.1 ppm

(Where data are unavailable an arbitrary score of 2 was allocated. For example, He is allocated a score of 2 since crustal abundance data is unavailable.)


Explanations for terminology


Crustal Abundance (ppm)

The abundance of an element in the Earth's crust in parts-per-million (ppm) i.e. The number of atoms of this element per 1 million atoms of crust.


Sourced

The country with the largest reserve base.


Reserve Base Distribution

This is a measure of the spread of future supplies, recording the percentage of a known resource likely to be available in the intermediate future (reserve base) located in the top three countries.


Production Concentrations

This reports the percentage of an element produced in the top three countries. The higher the value, the larger risk there is to supply.


Total Governance Factor

The World Bank produces a global percentile rank of political stability. The scoring system is given below, and the values for all three production countries were summed.


Relative Supply Risk Index

The Crustal Abundance, Reserve Base Distribution, Production Concentration and Governance Factor scores are summed and then divided by 2, to provide an overall Relative Supply Risk Index.

Supply Risk

 
Scarcity factor Unknown
Country with largest reserve base Unknown
Crustal abundance (ppm) Unknown
Leading producer Unknown
Reserve base distribution (%) Unknown
Production concentration (%) Unknown
Total governance factor(production) Unknown
Top 3 countries (mined)
  • Unknown
Top 3 countries (production)
  • Unknown
 

Oxidation states/ Isotopes


Key for Isotopes


Half Life
  y years
  d days
  h hours
  m minutes
  s seconds
Mode of decay
  α alpha particle emission
  β negative beta (electron) emission
  β+ positron emission
  EC orbital electron capture
  sf spontaneous fission
  ββ double beta emission
  ECEC double orbital electron capture

Terminology


Common Oxidation states
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. Free atoms have an oxidation state of 0, and the sum of oxidation numbers within a substance must equal the overall charge.


Important Oxidation states
The most common oxidation states of an element in its compounds.


Isotopes
Elements are defined by the number of protons in its centre (nucleus), whilst the number of neutrons present can vary. The variations in the number of neutrons will create elements of different mass which are known as isotopes.

Oxidation States / Isotopes

 
Common oxidation states 1
Isotopes Isotope Atomic mass Natural abundance (%) Half life Mode of decay
  133Cs 132.905 100
 

Pressure and Temperature - Advanced Terminology


Molar Heat Capacity (J mol-1 K-1)

Molar heat capacity is the energy required to heat a mole of a substance by 1 K.


Young's modulus (GPa)

Young's modulus is a measure of the stiffness of a substance, that is, 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.


Shear modulus (GPa)

The shear modulus of a material is a measure of how difficult it is to deform a material, and is given by the ratio of the shear stress to the shear strain.


Bulk modulus (GPa)

The bulk modulus is a measure of how difficult to compress a substance. Given by the ratio of the pressure on a body to the fractional decrease in volume.


Vapour Pressure (Pa)

Vapour pressure is the 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.

Pressure / Temperature - Advanced

 
Molar heat capacity
(J mol-1 K-1)
32.21 Young's modulus (GPa) Unknown
Shear modulus (GPa) Unknown Bulk modulus (GPa) 1.6
Vapour pressure  
Temperature (K)
400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
Pressure (Pa)
0.39 - - - - - - - - - -
  Help text not available for this section currently

History

Caesium was almost discovered by Carl Plattner in 1846 when he investigated the mineral pollucite (caesium aluminium silicate). He could only account for 93% of the elements it contained, but then ran out of material to analyse. (It was later realised that he mistook the caesium for sodium and potassium.)


Caesium was eventually discovered by Gustav Kirchhoff and Robert Bunsen in 1860 at Heidelberg, Germany. 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. The credit for that goes to Carl Theodor Setterberg at the University of Bonn who obtained it by the electrolysis of molten caesium cyanide, CsCN.

  Help text not available for this section currently

Podcasts

Listen to Caesium Podcast
Transcript :

Chemistry in its element - caesium


(Promo) 

You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry

(End promo) 

Meera Senthilingam 

 

This week, love at first sight. Peter Wothers.

 

Peter Wothers

 

I've been asked on a number of occasions what my favourite element is.   I used to think either oxygen or hydrogen - both so much fun - but that was until my sample of caesium arrived, when it was love at first sight.   Now many people think it's slightly odd having a favourite element, but when they too see my caesium, they understand why it's so special.   Who wouldn't be attracted to this beautiful element?

 

For starters, there are only three metallic elements that are not silver-coloured.   Two are well-known and fairly obvious - gold and copper.   The third most people would never guess, it's caesium.   Apparently, the beautiful gold diminishes if the sample is extremely pure since tiny traces of captured oxygen give it the colour.   This is a little disappointing - its colour is quite stunning and I would be sad if it really did disappear when purified. 

 

The next exciting thing about caesium is that my love is not unrequited, it responds to my touch.   Strictly speaking, it's the warmth from the hand that melts it, given that its melting point is only 28.4 °C. So just holding its container converts the crystalline solid into liquid gold.   Liquid metals are always fascinating - everyone loves mercury; just imagine playing with liquid gold!

 

But here's the snag that adds to my fascination with this metal - it has a rather fiery temper.   In fact, you can't actually touch the metal itself since it spontaneously bursts into flames in the presence of air and reacts explosively with water.   Awkward indeed.   My caesium is sealed inside a glass tube under an atmosphere of the chemically inert gas argon.   So to play with it, you have to hold the glass tube, knowing that if you accidentally crushed it, or dropped it, all hell would break loose.

 

Caesium gets its name from the Greek for heavenly blue.   Not for its eyes (it's only an element!) but less romantically for the appearance of its emission spectrum in the spectroscope.   Caesium was discovered in 1860 by Robert Bunsen (he of the burner fame) and physicist Gustav Kirchhoff.   The previous year they had invented an instrument known as a spectroscope to help in chemical analysis.   When atoms are energetically excited, for instance when a compound is introduced into a flame, electrons can temporarily be promoted to higher energy levels.   When they return to their lower energy states, energy is released in the form of light.   The spectroscope splits up the light with a prism and reveals a spectrum consisting of series of sharp coloured lines.   Each element has its own unique spectrum of lines, like a rainbow barcode.   When examining the spectrum of the residue from some spa mineral water, Bunsen and Kirchhoff found a series of lines that did not correspond to any known element.   They named the new element caesium because of the distinct blue lines in the spectrum.

 

It is another electronic transition in caesium that gives us the most accurate clocks on earth.   So called caesium atomic clocks are accurate to one second in more than a million years and are used when precision timing is crucial, for instance in tracking the space shuttle.

 

It is its willingness to lose an electron completely and form a positively charge ion that makes caesium the most reactive metal in the periodic table, and yes I am including its relative francium!   All the alkali metals are reactive because they have one outermost electron which is easily removed but on moving down the group, the atoms get larger and larger and this outermost electron gets on average further and further away from the positively charged nucleus.   What's more, on moving across the periodic table, from group one with lithium, sodium, potassium etc to group two with beryllium, magnesium, calcium and so on, it becomes increasingly harder to remove the outermost electrons.   This means the element for which it is easiest to remove an electron and form a cation, is in the bottom left-hand corner of the periodic table, where caesium is found.

 

One pseudo-science programme on TV showed the reaction between water and the different group one alkali metals, namely lithium, sodium, potassium, rubidium and caesium.   At least that's what they said.   Actually, they faked the reaction of rubidium and caesium with water since they thought they were not spectacular enough for TV.   They also said that the element beneath caesium in the periodic table, francium, would be even more reactive.   They were wrong.   It turns out for really heavy elements, the electrons begin to get slightly harder to remove than expected.  

 

In order to understand why, you would need to take into account Einstein's relativistic effects.   Theory predicts that the atoms begin to get slightly smaller and that it is actually harder to remove the outermost electron from francium than it is for caesium.   Remarkably, this experiment has been carried out and the prediction has been confirmed.   This means that despite what you may hear, or might have expected, caesium is the most reactive metal.   This is great since francium can only be made in miniscule proportions and then only lasts for a few minutes so you'll never see any.   Caesium on the other hand, is readily obtainable, and in its protective environment will last forever.   This means we can actually see, hold and play with the most reactive metallic element that nature has given us.    It's gorgeous, but watch out, it bites!

 

Meera Senthilingam 

And having seen the melting of this element in action, I must admit it is rather beautiful. That was Cambridge University's Peter Wothers with the chemistry of his favourite element caesium. Is it your favourite yet? Well if not listen next week when we discover an element created by cold fusion. 

Eric Scerri

Bohrium is also special in another respect, as the first element to be synthesised by a cold - rather than hot - fusion process between two nuclei.   The idea is to make two nuclei collide at low excitation energies and consequently to capitalise on the reduced tendency of such combined atoms to disintegrate. The successful cold fusion synthesis of bohrium was first achieved in 1981 in Darmstadt, Germany, by the fusion of bismuth-209 with chromium-24 to form bohrium-262 with a half-life of about 85 milliseconds.   Since then many other isotopes of bohrium have been produced, including the longest lived isotope so far bohrium-270, with a half-life of 61 seconds. 

 

Meera Senthilingam 

And join UCLA's Eric Scerri for the chemistry created by this fusion in  next week's Chemistry in its element. Until then thank you for listening, I'm Meera Senthilingam.

(Promo) 

Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists dot com. There's more information and other episodes of Chemistry in its element on our website at chemistryworld dot org forward slash elements. 

(End promo)

  Help text not available for this section currently
  Help Text

Resources

Description :
A teaching resource on The Alkali Metals supported by video clips from the Royal Institution Christmas Lectures® 2012.
Description :
A look at the explosive reaction of Caesium with Water
Description :
A series of short, fun videos exploring the chemistry of the alkali metals, taken from a lecture by Dr. Peter Wothers at the University of Cambridge.
Description :
A series of short, fun videos exploring the chemistry of the alkali metals, taken from a lecture by Dr. Peter Wothers at the University of Cambridge.
Description :
A look at these reactive alkali metals
Description :
A look at the explosive reaction of Caesium with Water. An extended version of this spectacular reaction
 

Terms & Conditions


Images © Murray Robertson 1999-2011
Text © The Royal Society of Chemistry 1999-2011

Welcome to "A Visual Interpretation of The Table of Elements", the most striking version of the periodic table on the web. 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. You may browse, download or print out one copy of the material displayed on the Site for your personal, non-commercial, non-public use, but you must retain all copyright and other proprietary notices contained on the materials. You may not further copy, alter, distribute or otherwise use any of the materials from this Site without the advance, written consent of the RSC. The images may not be posted on any website, shared in any disc library, image storage mechanism, network system or similar arrangement. Pornographic, defamatory, libellous, scandalous, fraudulent, immoral, infringing or otherwise unlawful use of the Images is, of course, prohibited.


If you wish to use the Images in a manner not permitted by these terms and conditions please contact the Publishing Services Department by email. If you are in any doubt, please ask.


Commercial use of the Images will be charged at a rate based on the particular use, prices on application. In such cases we would ask you to sign a Visual Elements licence agreement, tailored to the specific use you propose.


The RSC makes no representations whatsoever about the suitability of the information contained in the documents and related graphics published on this Site for any purpose. All such documents and related graphics are provided "as is" without any representation or endorsement made and warranty of any kind, whether expressed or implied, including but not limited to the implied warranties of fitness for a particular purpose, non-infringement, compatibility, security and accuracy.


In no event shall the RSC be liable for any damages including, without limitation, indirect or consequential damages, or any damages whatsoever arising from use or loss of use, data or profits, whether in action of contract, negligence or other tortious action, arising out of or in connection with the use of the material available from this Site. Nor shall the RSC be in any event liable for any damage to your computer equipment or software which may occur on account of your access to or use of the Site, or your downloading of materials, data, text, software, or images from the Site, whether caused by a virus, bug or otherwise.


We hope that you enjoy your visit to this Site. We welcome your feedback.

References

 
Images:  Visual Elements © Murray Robertson 2011
Mining and Sourcing data:  British Geological Survey – natural environment research council.
Text:  John Emsley Nature’s Building Blocks: An A-Z Guide to the Elements, Oxford University Press, 2nd Edition, 2011.
Additional information for platinum, gold, neodymium and dysprosium obtained from Material Value Consultancy Ltd www.matvalue.com
Data: CRC Handbook of Chemistry and Physics, CRC Press, 92nd Edition, 2011.
G. W. C. Kaye and T. H. Laby Tables of Physical and Chemical Constants, Longman, 16th Edition, 1995.
Members of the RSC can access these books through our library.