99
Es
Actinide

Einsteinium

Atomic number 99 · Period 7 · Block F

Es · Einsteinium
Mendeleev.com

Understanding the element

Einsteinium (Es) is chemical element 99. It belongs to the actinoids, 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 scientific research.

scientific research
Standard atomic weightNo standard atomic weight

What its position in the table tells us

Einsteinium sits in period 7 and the F block. That location is useful because neighbouring elements often share trends in valence electrons, oxidation states and bonding behaviour.

Worth remembering
Einsteinium is radioactive, so its chemistry cannot be separated from nuclear physics and radiation safety

Scientific sources

Element identity
Atomic number99
Group
Period7
BlockF
CategoryActinide
PhaseSolid