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Cobalt [Co] – Element Details, History, Atomic Structure, Facts, Properties, Electronic Configuration, Atomic Spectrum, Uses.


Element 27 of Periodic table is Cobalt with atomic number 27, atomic weight 58.9332. Cobalt, symbol Co, has a Simple Hexagonal structure and Gray color. Cobalt is a Transition Metal element. It is part of group 9 (cobalt family). Know everything about Cobalt Facts, Physical Properties, Chemical Properties, Electronic configuration, Atomic and Crystal Structure.

History of Cobalt

The element Cobalt was discovered by G. Brandt in year 1735 in Sweden. Cobalt was first isolated by G. Brandt in 1735. Cobalt derived its name from the German word Kobold, meaning ‘goblin’.

Proved that the blue color of glass is due to a new kind of metal and not bismuth as thought previously.

How to Locate Cobalt on Periodic Table

Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 27 to find Cobalt on periodic table.

Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Cobalt on periodic table look for cross section of group 9 and period 4 in the modern periodic table.

Cobalt Facts

Atomic Symbol
Atomic Number
Atomic Weight
Transition Metal
Group in Periodic Table
Group Name
Cobalt family
Block in Periodic Table
Period in Periodic Table
Electronic Configuration
[Ar] 3d7 4s2
Melting Point
1768 K
Boiling Point
3200 K
Electronic Shell Structure
[2, 8, 15, 2]
CAS Number

Cobalt Atomic Structure and Orbital Properties

Cobalt atoms have 27 electrons and the electronic shell structure is [2, 8, 15, 2] with Atomic Term Symbol (Quantum Numbers) 4F9/2.

Element Properties

Atomic Number
Number of Protons
Mass Number
Number of Neutrons
Shell structure (Electrons per energy level)
[2, 8, 15, 2]
Electron Configuration
[Ar] 3d7 4s2
Valence Electrons
3d7 4s2
Oxidation State
-3, -1, 0, 1, 2, 3, 4, 5
Atomic Term Symbol (Quantum Numbers)


Atomic Structure of Cobalt

Atomic Radius
152 pm (1.52 Å)
Atomic Radius Empirical
135 pm (1.35 Å)
Atomic Volume
6.62 cm3/mol
Covalent Radius
126 pm (1.26 Å)
Van der Waals Radius
Neutron Cross Section
Neutron Mass Absorption

Crystal Structure of Cobalt

The solid state structure of Cobalt is Simple Hexagonal.

The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.

The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a[250.71 pm]b[250.71 pm] and c[406.95 pm]) and the angles between them Lattice Angles (alpha[π/2], beta[π/2] and gamma[2π/3])

The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.

The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.

Space Group Name

Space Group Number

Crystal Structure



Simple Hexagonal

Ground State Electronic Configuration of Cobalt- neutral Cobalt atom

Abbreviated electronic configuration of Cobalt

The ground state abbreviated electronic configuration of Neutral Cobalt atom is [Ar] 3d7 4s2. The portion of Cobalt configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Ar]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 3d7 4s2, electrons in the outermost shell that determine the chemical properties of the element.

Unabbreviated electronic configuration of neutral Cobalt

Complete ground state electronic configuration for the Cobalt atom, Unabbreviated electronic configuration

1s2 2s2 2p6 3s2 3p6 3d7 4s2

Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.

  • As per the Aufbau principle the electrons will occupy the orbitals having lower energies before occupying higher energy orbitals. According to this principle, electrons are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
  • The Pauli exclusion principle states that a maximum of two electrons, each having opposite spins, can fit in an orbital.
  • Hund’s rule states that every orbital in a given subshell is singly occupied by electrons before a second electron is filled in an orbital.

Regulatory and Health - Health and Safety Parameters and Guidelines

CAS Number
RTECS Number
EU Number
DOT Hazard Class
DOT Numbers
NFPA Fire Rating
NFPA Hazards
Autoignition Point
NFPA Health Rating
NFPA Reactivity Rating

Cobalt Chemical Properties : Cobalt Ionization Energies and electron affinity

63.7 kJ/mol

Cobalt Physical & Elastic Properties

8.9 g/cm3(when liquid at m.p density is $7.75 g/cm3)
Molar Volume
6.62 g/cm3
Young Modulus
Shear Modulus
75 GPa
Bulk Modulus
180 GPa
Poisson Ratio

Cobalt Electrical Properties

Electrical Conductivity
17000000 S/m
6e-8 m Ω
Superconducting Point

Cobalt Magnetic Properties

Magnetic Type
Curie Point
1394 K
Mass Magnetic Susceptibility
Molar Magnetic Susceptibility
Volume Magnetic Susceptibility

Cobalt Thermal Properties

Melting Point
1768 K (1494.85°C, 2722.73 °F)
Boiling Point
3200 K (2926.85°C, 5300.33 °F)
Critical Temperature
Superconducting Point

Use of Cobalt

Cobalt can be magnetized, for this property it used to make magnets. Cobalt is alloyed with Aluminium and nickel to create  powerful magnets. Cobalt alloys are used in jet turbines and gas turbine generators in high-temperature strength.

106. Seaborgium [Sg]