99
Es
Einsteinium
252
Einsteinium
ACTINIDE
Bohr Model: Electrons arranged in energy shells around the nucleus.
Einsteinium is a synthetic element with symbol Es and atomic number 99. It is the seventh transuranic element, and an actinide. Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after Albert Einstein.
Quick Facts
Atomic Number 99
Period 7
Group 13
Phase Solid
Appearance silver-colored
About Actinides
Actinides are the 15 metallic elements with atomic numbers 89–103. All actinides are radioactive.
History
Discovered By Lawrence Berkeley National Laboratory
Named By Unknown
Physical Properties
Atomic Mass 252
Density 8.84 g/L
Molar Heat N/A J/(mol·K)
Phase Transition (Melting & Boiling Points)
Einsteinium melts at 1133 K and boils at 1269 K.
Atomic Properties
Electron Config [Rn] 5f11 7s2
Electronegativity 1.3
Electron Affinity -28.6 kJ/mol
Ionization Energy 619 kJ/mol
Orbital Filling Diagram
This diagram visualizes electron configuration according to the Aufbau principle and Hund's rule.
Boxes represent orbitals (s, p, d, f), while arrows indicate electrons with spin up or down.
Electrons fill lower energy levels first and occupy orbitals singly before pairing.
Photograph
External Resources
Study Guide
Atomic Number
The number of protons in the nucleus, which defines the element.
Atomic Mass
The average mass of an atom, including protons and neutrons.
Electronegativity
A measure of how strongly an atom attracts electrons in a bond.
Ionization Energy
The energy required to remove an electron from an atom.
Electron Config
The arrangement of electrons in the atom's energy shells.