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cobalt
Image: Wikimedia Commons

cobalt

Chemical element with symbol Co and atomic number 27

Chemical elementchemical elementQ740

Also known as ₂₇Co · Co · element 27

Symbol
Atomic number
  • 27
Mass
Melting point
Boiling point
Density
  • 8.92 g/cm³
Discovered by
Discovered
  • 1735

Overview

All data

299 statements · 13% with external sources · numbers in brackets are citations

Oxidation state
  • 2
  • 3
  • -1
  • 1
  • 4
  • 5
  • -3
  • 0
Named after
NIOSH Pocket Guide ID
  • 0146
Has effect
Immediately dangerous to life or health
  • 20 milligram per cubic metre
Vapor pressure
  • 0 millimetre of mercury temperature: 68°F
Time-weighted average exposure limit
  • 0.05 milligram per cubic metre applies to jurisdiction: none · runtime: 10 h
  • 0.1 milligram per cubic metre applies to jurisdiction: United States · runtime: 8 h
Subject has role
Has characteristic
Unicode character
Electronegativity
  • 1.88
Part of
Ionic radius
  • 0.56 ångström charge number: 2 · coordination number: 4
  • 0.65 ångström charge number: 2 · coordination number: 6
  • 0.9 ångström charge number: 2 · coordination number: 8
  • 0.55 ångström charge number: 3 · coordination number: 6
Electron configuration
  • [Ar] 3d⁷ 4s²
Subclass of
Associated hazard
Made from material
Space group
Crystal system
Bulk modulus
  • 201B Pa
Shear modulus
  • 120B Pa
Poisson's ratio
  • 0.25
Thermal conductivity
  • 100 watt per metre kelvin
Electrical conductivity
  • 16.7M siemens per metre
Specific heat capacity
  • 421 joule per kilogram kelvin
Speed of sound
  • 4,720 m/s
Electrical resistivity
  • 6.24e-8 ohm metre
Point group
Standard enthalpy of formation
  • 426.68 kilojoule per mole state of matter: gas
  • 18 kilojoule per mole state of matter: liquid
Standard molar entropy
  • 179.51 joule per mole kelvin state of matter: gas
  • 41 joule per mole kelvin state of matter: liquid
  • 30.07 joule per mole kelvin state of matter: solid
Mohs' hardness
  • 5
Ionization energy
IPA transcription
Atomic radius
  • 135 picometre
Covalent radius
  • 138 picometre

On other databases

92 identifiers linking cobalt across the web's reference databases