# Caesium
## ๐ง Caesium ยท 3D (three.js)
<iframe src="https://wikitube-elements.netlify.app/?el=Cs&embed=1" width="100%" height="620" frameborder="0" style="border:0;border-radius:12px;overflow:hidden" allowfullscreen loading="lazy" title="The Elements 3D microsim - Caesium"></iframe>
*Caesium in the live three.js Elements explorer โ drag to orbit the atom, click any tile to compare, slide the temperature.* ยท [โถ open full](https://wikitube-elements.netlify.app/?el=Cs)
<!-- ELEMENTS_MICROSIM:END -->
!Caesium plate.svg
*Plate 55 of 118 - animated Bohr shells, stylized per Madelung filling; engraving style per house Arcanity kit.*
## Microsim To Do
*Claimable rows, house pattern. Real Wikipedia articles only.*
- Caesium atom clock - atomic frequency standard
- Caesium-137 - fission product and radiotherapy
- Spectroscopy - discovery and spectral lines
- Alkali metal - chemical reactivity and properties
## Links (Wikipedia order)
<!-- injected from _registry/childlinks/Caesium.json (2026-07-30T02:09:12Z) -->
`Abundance_of_elements_in_Earth's_crust` ยท `Acerinox_accident` ยท `Acetate` ยท `Acrylic_acid` ยท [[Actinium]] ยท `Alkali_metal` ยท `Alkalide` ยท `Alkaline_earth_metal` ยท `Alkene` ยท `Allotropy` ยท [[Alloy]] ยท `Alum` ยท [[Aluminium]] ยท `Aluminium_oxide` ยท `Aluminium_sulfate` ยท `Amalgam_(chemistry)` ยท `American_Chemical_Society` ยท `American_English` ยท `American_and_British_English_spelling_differences` ยท [[Americium]] ยท `Ammonia` ยท `Ammonium_carbonate` ยท `Ampoule` ยท `Angewandte_Chemie` ยท `Anhydrous` ยท `Annalen_der_Physik` ยท `Anode` ยท `Anthraquinone` ยท [[Antimony]] ยท [[Argon]] ยท [[Arsenic]] ยท [[Astatine]] ยท `Atmosphere_of_Earth` ยท `Atomic_clock` ยท `Atomic_emission_spectroscopy` ยท [[Atomic_mass]] ยท `Atomic_number` ยท `Atomic_radius` ยท `Aulus_Gellius` ยท `Autoignition_temperature` ยท `Avogadrite` ยท `Azide` ยท `Bad_Dรผrkheim` ยท [[Barium]] ยท `Barium_azide` ยท `Base_(chemistry)` ยท `Becquerel` ยท [[Berkelium]] ยท `Bernic_Lake` ยท `Beryl` ยท [[Beryllium]] ยท [[Beta_decay]] ยท `Bikita_District` ยท `Biosphere` ยท [[Bismuth]] ยท `Block_(periodic_table)` ยท [[Bohrium]] ยท [[Boiling_point]] ยท [[Boron]] ยท `Boron_group` ยท `Borosilicate_glass` ยท `Brinell_hardness_test` ยท [[Bromine]] ยท `Brookhaven_National_Laboratory` ยท `BrรธnstedโLowry_acidโbase_theory` ยท `Bulk_modulus` ยท `CAS_Registry_Number` ยท `CRC_Handbook_of_Chemistry_and_Physics` ยท `CRC_Press` ยท `Cabot_Corporation` ยท [[Cadmium]] ยท `Cadmium_chloride` ยท `Caesium-137` ยท `Caesium_acetate` ยท `Caesium_auride` ยท `Caesium_azide` ยท `Caesium_bicarbonate` ยท `Caesium_bisulfate` ยท `Caesium_bromide` ยท `Caesium_carbonate` ยท `Caesium_chloride` ยท `Caesium_chromate` ยท `Caesium_cyanide` ยท `Caesium_dibismuthide` ยท `Caesium_dodecaborate` ยท `Caesium_enneabromodibismuthate` ยท `Caesium_fluoride` ยท `Caesium_fluoroaluminate` ยท `Caesium_heptafluoroxenate` ยท `Caesium_hexafluorocobaltate(IV)` ยท `Caesium_hexafluorocuprate(IV)` ยท `Caesium_hydride` ยท `Caesium_hydroxide` ยท `Caesium_iodide` ยท `Caesium_lithium_borate` ยท `Caesium_monoxide` ยท `Caesium_nitrate` ยท `Caesium_oxalate` ยท `Caesium_oxide` ยท `Caesium_ozonide` ยท `Caesium_perchlorate` ยท `Caesium_permanganate` ยท `Caesium_peroxide` ยท `Caesium_pertechnetate` ยท `Caesium_phosphide` ยท `Caesium_selenate` ยท `Caesium_selenide` ยท `Caesium_sesquioxide` ยท `Caesium_standard` ยท `Caesium_stearate` ยท `Caesium_sulfate` ยท `Caesium_sulfide` ยท `Caesium_superoxide` ยท `Caesium_titanate` ยท `Caesium_tribromide` ยท `Caesium_triiodide` ยท `Caesium_tungstate` ยท `Caesium_zirconate` ยท [[Calcium]] ยท `Calcium_carbonate` ยท `Calcium_chloride` ยท [[Californium]] ยท [[Carbon]] ยท `Carbon_group` ยท `Carbon_nanotube` ยท `Carbonate` ยท `Cardiac_arrest` ยท `Carl_Setterberg` ยท `Carnallite` ยท `Carol_Kendall_(scientist)` ยท `Cathode` ยท [[Cerium]] ยท `Chalcogen` ยท [[Chemical_element]] ยท `Chernobyl_disaster` ยท [[Chlorine]] ยท `Chloroplatinic_acid` ยท [[Chromium]] ยท [[Cobalt]] ยท `Colloid` ยท `Commission_on_Isotopic_Abundances_and_Atomic_Weights` ยท `Completion_(oil_and_gas_wells)` ยท `Coordination_number` ยท [[Copernicium]] ยท [[Copper]] ยท `Covalent_radius` ยท `Critical_point_(thermodynamics)` ยท [[Crystal_structure]] ยท [[Cubic_crystal_system]] ยท `Curie_(unit)` ยท [[Curium]] ยท `Cyanide` ยท `Cyclic_compound` ยท [[Darmstadtium]] ยท [[Decay_product]] ยท `Deep_Space_1` ยท [[Density]] ยท `Dicaesium_hexachloroplutonate` ยท `Dicaesium_silver_hexabromobismuthate` ยท `Dirty_bomb` ยท `Dosimetry` ยท `Double_salt` ยท `Drilling_fluid` ยท [[Dubnium]] ยท `Ductility` ยท [[Dysprosium]] ยท [[Einsteinium]] ยท `Electrical_resistivity_and_conductivity` ยท `Electrolysis` ยท `Electromagnetic_radiation` ยท [[Electron]] ยท `Electron_capture` ยท `Electron_configuration` ยท `Electron_density` ยท `Electronegativity` ยท `Emission_spectrum` ยท `Energy_level` ยท `Enthalpy_of_fusion` ยท `Enthalpy_of_vaporization` ยท `Epilepsy` ยท [[Erbium]] ยท `Erongo_Region` ยท `Etching` ยท `Ethanol` ยท `Ethylene_oxide` ยท [[Europium]] ยท `Exhaust_gas` ยท [[Fermium]] ยท `Feshbach_resonance` ยท `Field-emission_electric_propulsion` ยท `Fission_product_yield` ยท [[Flerovium]] ยท `Fluorescent_lamp` ยท `Fluoride` ยท [[Fluorine]] ยท `Formate` ยท `Formic_acid` ยท `Fractional_crystallization_(chemistry)` ยท `Fractional_crystallization_(geology)` ยท [[Francium]] ยท `Frequency` ยท `GHS_hazard_pictograms` ยท `GHS_hazard_statements` ยท `GHS_precautionary_statements` ยท [[Gadolinium]] ยท [[Gallium]] ยท `Gamma_ray` ยท `General_Conference_on_Weights_and_Measures` ยท [[Germanium]] ยท `Getter` ยท `Globally_Harmonized_System_of_Classification_and_Labelling_of_Chemicals` ยท `Goiรขnia_accident` ยท [[Gold]] ยท `Ground_state` ยท `Group_(periodic_table)` ยท `Group_10_element` ยท `Group_11_element` ยท `Group_12_element` ยท `Group_3_element` ยท `Group_4_element` ยท `Group_5_element` ยท `Group_6_element` ยท `Group_7_element` ยท `Group_8_element` ยท `Group_9_element` ยท `Gustav_Kirchhoff` ยท `HSAB_theory` ยท [[Hafnium]] ยท [[Half-life]] ยท `Halide` ยท `Halogen` ยท [[Hassium]] ยท [[Helium]] ยท `Hermetic_seal` ยท [[Holmium]] ยท `Hydrobromic_acid` ยท `Hydrochloric_acid` ยท `Hydrofluoric_acid` ยท [[Hydrogen]] ยท `Hydrology` ยท `Hydroxide` ยท `Hyperfine_structure` ยท `Hypokalemia` ยท `Incompatible_element` ยท [[Indium]] ยท [[Inert_gas]] ยท `Infrared` ยท `Infrared_spectroscopy` ยท `Internal_standard` ยท `International_Atomic_Energy_Agency` ยท `International_System_of_Units` ยท `International_Union_of_Pure_and_Applied_Chemistry` ยท [[Iodine]] ยท `Ion_thruster` ยท `Ionic_radius` ยท [[Ionization_energy]] ยท [[Iridium]] ยท [[Iron]] ยท `Isotope` ยท `Isotopes_of_barium` ยท `Isotopes_of_caesium` ยท `Isotopes_of_iodine` ยท `Isotopes_of_xenon` ยท `Journal_of_Chemical_Education` ยท `Kelvin` ยท `Kramatorsk_radiological_accident` ยท [[Krypton]] ยท [[Lanthanum]] ยท `Laser` ยท `Laser_cooling` ยท `Latin` ยท `Lattice_constant` ยท [[Lawrencium]] ยท `Leaching_(metallurgy)` ยท [[Lead]] ยท `Lepidolite` ยท `Liquid` ยท `List_of_chemical_element_name_etymologies` ยท `List_of_data_references_for_chemical_elements` ยท [[Lithium]] ยท [[Livermorium]] ยท `Lockheed_A-12` ยท `Long-lived_fission_product` ยท `Louis_Essen` ยท `Lustre_(mineralogy)` ยท [[Lutetium]] ยท [[Magnesium]] ยท `Magnetism` ยท `Magnetometer` ยท [[Manganese]] ยท `Manitoba` ยท `Mary_Elvira_Weeks` ยท `Mass_number` ยท `Median_lethal_dose` ยท [[Meitnerium]] ยท `Melting_point` ยท [[Mendelevium]] ยท [[Mercury_(element)]] ยท `Metal` ยท `Methanol` ยท `Methyl_methacrylate` ยท `Microwave` ยท `Mineral_oil` ยท `Mineral_water` ยท `Mohs_scale` ยท `Molar_concentration` ยท `Molar_heat_capacity` ยท [[Molybdenum]] ยท [[Moscovium]] ยท `NFPA_704` ยท `Namibia` ยท `Nanosecond` ยท `National_Nuclear_Data_Center` ยท `Natural_abundance` ยท `Nature_(journal)` ยท [[Neodymium]] ยท [[Neon]] ยท [[Neptunium]] ยท [[Neutron]] ยท `Neutron_capture` ยท `Neutron_poison` ยท [[Nickel]] ยท `Night_vision` ยท `Nigidius_Figulus` ยท [[Nihonium]] ยท [[Niobium]] ยท `Nitrate` ยท [[Nitrogen]] ยท [[Nobelium]] ยท [[Noble_gas]] ยท `Non-stoichiometric_compound` ยท `Nuclear_fallout` ยท `Nuclear_fission` ยท `Nuclear_fuel_cycle` ยท `Nuclear_isomer` ยท [[Nuclear_magnetic_resonance]] ยท `Nuclear_weapons_testing` ยท `Nucleic_acid` ยท [[Oganesson]] ยท `Optical_character_recognition` ยท `Optical_fiber` ยท `Organelle` ยท `Organic_chemistry` ยท `Organic_synthesis` ยท `Organofluorine_chemistry` ยท [[Osmium]] ยท `Oxalate` ยท `Oxford_English_Dictionary` ยท `Oxidation_state` ยท `Oxide` ยท `Oxidizing_agent` ยท [[Oxygen]] ยท `Ozonide` ยท [[Palladium]] ยท `Pascal_(unit)` ยท `Pearson_symbol` ยท `Pegmatite` ยท `Period_(periodic_table)` ยท `Period_1_element` ยท `Period_2_element` ยท `Period_3_element` ยท `Period_4_element` ยท `Period_5_element` ยท `Period_6_element` ยท `Period_7_element` ยท `Periodic_table` ยท `Peroxide` ยท `Petalite` ยท `Petr_ฤernรฝ` ยท `Pezzottaite` ยท `Phase_(matter)` ยท `Phosphate` ยท [[Phosphorus]] ยท `Photoelectric_effect` ยท `Photomultiplier` ยท `Photomultiplier_tube` ยท `Phototube` ยท `Phthalic_anhydride` ยท `Picometre` ยท `Plasma_oscillation` ยท [[Platinum]] ยท [[Plutonium]] ยท `Pnictogen` ยท `Pollucite` ยท [[Polonium]] ยท `Polymerization` ยท [[Potassium]] ยท `Potassium_chloride` ยท [[Praseodymium]] ยท `Primordial_nuclide` ยท [[Promethium]] ยท [[Protactinium]] ยท `Pseudohalogen` ยท `Pyrophoricity` ยท `Pyrotechnic_colorant` ยท [[Quantum_mechanics]] ยท `Radiation_therapy` ยท [[Radioactive_decay]] ยท `Radionuclide` ยท [[Radium]] ยท [[Radon]] ยท `Rankine_cycle` ยท `Rectifier` ยท [[Rhenium]] ยท [[Rhodium]] ยท `Robert_Bunsen` ยท [[Roentgenium]] ยท `Room_temperature` ยท `Royal_Society_of_Chemistry` ยท [[Rubidium]] ยท `Rubidium_chloride` ยท [[Ruthenium]] ยท [[Rutherfordium]] ยท `SI_base_unit` ยท [[Samarium]] ยท [[Scandium]] ยท `Scintillation_counter` ยท `Scintillator` ยท [[Seaborgium]] ยท `Second` ยท [[Selenium]] ยท `Semiconductor` ยท `Silicate` ยท [[Silicon]] ยท [[Silver]] ยท [[Sodium]] ยท `Sodium_amide` ยท `Sodium_chloride` ยท `Sodium_hydride` ยท `Solar_cell` ยท `Solid` ยท `Spacecraft_propulsion` ยท `Specific_heat_capacity` ยท `Spectral_line` ยท `Spectrophotometry` ยท `Spectroscopy` ยท `Spent_nuclear_fuel` ยท `Stable_nuclide` ยท `Standard_atomic_weight` ยท `Standard_temperature_and_pressure` ยท `Sterilization_(microbiology)` ยท `Stoichiometry` ยท [[Strontium]] ยท `Strontium-90` ยท `Styrene` ยท `Suboxide` ยท `Sulfate` ยท [[Sulfur]] ยท `Sulfur_dioxide` ยท `Sulfur_trioxide` ยท `Sulfuric_acid` ยท `Superoxide` ยท `Sylvite` ยท `Synthetic_radioisotope` ยท `Tanco_Mine` ยท [[Tantalum]] ยท [[Technetium]] ยท [[Tellurium]] ยท [[Tennessine]] ยท [[Terbium]] ยท `Tetramethylammonium_auride` ยท [[Thallium]] ยท `Thermionic_converter` ยท [[Thorium]] ยท [[Thulium]] ยท `Timeline_of_chemical_element_discoveries` ยท [[Tin]] ยท [[Titanium]] ยท `Tonne` ยท `Toxicology_and_Applied_Pharmacology` ยท `Trace_radioisotope` ยท `Transition_metal` ยท `Transmission_electron_microscopy` ยท `Trifluoroacetic_acid` ยท `Tritium` ยท `Triveni_Rao` ยท [[Tungsten]] ยท `Ultracold_atom` ยท [[Uranium]] ยท `Vacuum_tube` ยท `Van_der_Waals_radius` ยท [[Vanadium]] ยท `Vapor_pressure` ยท `Video_camera_tube` ยท `Virus` ยท `Water` ยท [[Wayback_Machine]] ยท `Well_logging` ยท `X-ray` ยท [[Xenon]] ยท `Xenon-135` ยท `Young's_modulus` ยท [[Ytterbium]] ยท [[Yttrium]] ยท `Zimbabwe` ยท [[Zinc]] ยท `Zinc_bromide` ยท [[Zirconium]] ยท `ร`
> **Official MAIN - Chemical element, Z = 55.** Part of the Elements Canon (one canonical page per element). Infobox grounded in [Wikipedia: List of chemical elements](https://en.wikipedia.org/wiki/List_of_chemical_elements), fetched 2026-07-08. Full article: [Wikipedia: Caesium](https://en.wikipedia.org/wiki/Caesium).
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## Key facts (infobox)
| | |
|---|---|
| Symbol - Z | Cs - 55 |
| Group - Period - Block | 1 - 6 - s-block |
| Atomic weight (Da) | 132.91 |
| Density (g/cm3) | 1.93 |
| Melting - Boiling (K) | 301.59 - 944 |
| Electronegativity (Pauling) | 0.79 |
| Crustal abundance (mg/kg) | 3 |
| Origin | primordial |
| Phase (STP) | solid |
| Name origin | Latin caesius, 'sky-blue' |
*Bracketed weights are the mass number of the most stable isotope; values in parentheses are predictions (per the source table).*
## Story
Caesium was discovered in 1860 by German chemists Robert Bunsen and Gustav Kirchhoff through spectroscopic analysis of mineral spring water. It was the first element discovered using spectroscopy. The name derives from Latin caesius, meaning sky-blue, referring to the characteristic blue spectral lines. Caesium is moderately scarce (3 mg/kg) and occurs in the mineral pollucite and in brines.
Caesium is the most electropositive metal and the most reactive of the stable alkali metals. It is stored under mineral oil because it reacts violently with water, oxygen, and halogens. [model-prior - verify] Caesium's most important application is in caesium atomic clocks, which define the international standard second; they achieve frequencies accurate to better than one part in 10ยนโต. [model-prior - verify] Caesium-137, a fission product, is used in medical radiotherapy (brachytherapy) and industrial radiography, though it is also a concern in nuclear waste. [model-prior - verify]
The corpus engages caesium through its fundamental role in timekeeping standards and its dual nature as both a scientific tool and a nuclear hazard.
## Corpus connections
- R.E.A.C.T.I.O.N. - the Chemistry hub
- Centers of Excellence Portal
- [[Technetium|Technetium - the element made before found]] - the canon's patron - and Technitium, the School
- Solar System Mining Surveys - caesium's role in fundamental timekeeping
## Vocational-Technical Semiotics
The element speaks the canon's shared signs: the periodic table cell (Cs, group 1, period 6), isotope notation, and hazard pictograms ghs where handling demands it.
## Sources
Infobox: [en.wikipedia.org/wiki/List_of_chemical_elements](https://en.wikipedia.org/wiki/List_of_chemical_elements) (fetched 2026-07-08); etymology per the same table's notes. Story sources to be added at enrichment.
## Navigation
- Canon: Elements Canon index - neighbors by Z: [[Xenon|Xenon (54)]] - [[Barium|Barium (56)]]
- R.E.A.C.T.I.O.N. - Centers of Excellence
## Wikipedia : Wikitube
**Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Caesium) : [Wikitube](https://en.wikitube.io/wiki/Caesium)
## Previous hub tags
Tree parents: [[Helium]] ยท [[Helium-3]] ยท [[Hydrogen]] ยท [[Oxygen]].
Legacy hubs: none.
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*Sources: 1 legacy note. Minted wave 1, 2026-07-30 (v1.6 order).*