Einsteinium (Es)

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.

Atomic Number

Atomic Mass

252 u

Phase

solid

Density

8.84 g/cm³

Electron Shells

2, 8, 18, 32, 29, 8, 2

Atomic Structure

Protons: 99 • Electrons: 99 • Neutrons: Varies by isotope

Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹¹

Discovery

1952 • Albert Ghiorso, Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey