Template:Infobox caesium

Caesium, ₅₅Cs

Some pale gold metal, with a liquid-like texture and lustre, sealed in a glass ampoule
Caesium
Pronunciation	/ˈsiːziəm/ ​(SEE-zee-əm)
Alternative name	cesium (US)
Appearance	pale gold
Standard atomic weight Ar°(Cs)
	132.90545196±0.00000006 132.91±0.01 (abridged)
Caesium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Rb ↑ Cs ↓ Fr xenon ← caesium → barium
Atomic number (Z)	55
Group	group 1: hydrogen and alkali metals
Period	period 6
Block	s-block
Electron configuration	[Xe] 6s1
Electrons per shell	2, 8, 18, 18, 8, 1
Physical properties
Phase at STP	solid
Melting point	301.7 K ​(28.5 °C, ​83.3 °F)
Boiling point	944 K ​(671 °C, ​1240 °F)
Density (at 20° C)	1.886 g/cm3
when liquid (at m.p.)	1.843 g/cm3
Critical point	1938 K, 9.4 MPa
Heat of fusion	2.09 kJ/mol
Heat of vaporization	63.9 kJ/mol
Molar heat capacity	32.210 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 418 469 534 623 750 940
Atomic properties
Oxidation states	common: +1 −1
Electronegativity	Pauling scale: 0.79
Ionization energies	1st: 375.7 kJ/mol 2nd: 2234.3 kJ/mol 3rd: 3400 kJ/mol
Atomic radius	empirical: 265 pm
Covalent radius	244±11 pm
Van der Waals radius	343 pm
Color lines in a spectral range Spectral lines of caesium
Other properties
Natural occurrence	primordial
Crystal structure	​body-centered cubic (bcc) (cI2)
Lattice constant	Bodycentredcubic crystal structure for caesium a = 616.2 pm (at 20 °C)
Thermal expansion	92.6×10−6/K (at 20 °C)
Thermal conductivity	35.9 W/(m⋅K)
Electrical resistivity	205 nΩ⋅m (at 20 °C)
Magnetic ordering	paramagnetic
Young's modulus	1.7 GPa
Bulk modulus	1.6 GPa
Mohs hardness	0.2
Brinell hardness	0.14 MPa
CAS Number	7440-46-2
History
Naming	from Latin caesius 'bluish grey', for its spectral colours
Discovery	Robert Bunsen and Gustav Kirchhoff (1860)
First isolation	Carl Setterberg (1882)
Isotopes of caesium
Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 131Cs synth 9.7 d ε 131Xe 133Cs 100% stable 134Cs synth 2.0648 y ε 134Xe β− 134Ba 135Cs trace 1.33×106 y β− 135Ba 137Cs synth 30.04 y β− 137Ba

Cs · Caesium
Xe ← ibox Xe	iso 55 Cs  [] IB-Cs [] IBisos []	→ Ba ibox Ba
File:Symbol category class.svg cat:Cs (0) File:Symbol category class.svg cat:Cs-isotopes (0) File:Commons-logo.svg Commons File:Wikidata-logo.svg Wikidata:Q1108 File:Wiktionary-logo.svg Wiktionary
indexes by PT (page)

child table, as reused in {IB-Cs}
Main isotopes of caesium
Main isotopes Decay abun­dance half-life (t1/2) mode pro­duct 131Cs synth 9.7 d ε 131Xe 133Cs 100% stable 134Cs synth 2.0648 y ε 134Xe β− 134Ba 135Cs trace 1.33×106 y β− 135Ba 137Cs synth 30.04 y β− 137Ba

Data sets read by {{Infobox element}}
Name and identifiers
Symbol etymology (11 non-trivial)
Top image (caption, alt)	caption: alt:
Pronunciation
Allotropes (overview)
Group (overview)
Period (overview)
Block (overview)
Natural occurrence
Phase at STP
Oxidation states
Spectral lines image
Electron configuration (cmt, ref)
Isotopes
Standard atomic weight
most stable isotope
File:Notification-icon-Wikidata-logo.svg Wikidata
Wikidata *
* Not used in {{Infobox element}} (2023-01-01) See also {{Index of data sets}} · Cat:data sets (0) · (this table: )

References

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