27
Co
Transition metal

Cobalt

Atomic number 27 · Period 4 · Block D

Co · Cobalt
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Understanding the element

Cobalt (Co) is chemical element 27. It belongs to the transition metals, and its reference state at room temperature is a solid. Those basic facts are a useful starting point for its chemistry and applications.

Where do we encounter it?

In practice, it turns up most often in batteries, superalloys and pigments.

batteriessuperalloyspigments
Standard atomic weight58.933194(3)

What its position in the table tells us

Cobalt sits in period 4, group 9 and the D block. That location is useful because neighbouring elements often share trends in valence electrons, oxidation states and bonding behaviour.

Worth remembering
Cobalt has a characteristic place in the periodic table that helps explain both its chemistry and its practical uses

Scientific sources

Element identity
Atomic number27
Group9
Period4
BlockD
CategoryTransition metal
PhaseSolid