Element 27
Cobalt
Transition metals
Cobalt (Co) is in the d-block of the periodic table — group 9, period 4.
Cobalt is a chemical element with symbol Co and atomic number 27.
Key data
- Atomic number
- 27
- Atomic mass
- 58.933 u
- Group / Period
- 9 / 4
- Block
- d-block
- Phase at STP
- Solid
- Density
- 8.9 g/cm³
- Melting point
- 1494.8 °C
- Boiling point
- 2926.8 °C
- Electron configuration
- [Ar] 3d7 4s2
Periodic table block
Cobalt is in the d-block (group 9, period 4). Elements land in the d-block when their highest-energy electrons fill a d subshell — these are the transition metals in the middle of the table.
New to this? Periodic table blocks explained: s, p, d, and f
Common uses
- •Lithium batteries
- •Magnets
- •Vitamin B12
Discovery
Year: 1735
Discovered by: Georg Brandt
Frequently asked questions
What is the atomic number of Cobalt?
Cobalt has atomic number 27. Its symbol is Co and its atomic mass is 58.933 u.
What category of element is Cobalt?
Cobalt is classified as transition metals. It sits in group 9, period 4 of the periodic table.
What block of the periodic table is Cobalt in?
Cobalt is in the d-block (group 9, period 4). Its highest-energy electrons occupy the d subshell — you can see this in its electron configuration, [Ar] 3d7 4s2.
What is Cobalt used for?
Common uses of Cobalt include: Lithium batteries, Magnets, Vitamin B12.
When was Cobalt discovered?
Cobalt was discovered in 1735 by Georg Brandt.
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