What is the atomic number of Einsteinium?

Einsteinium has atomic number 99, which means a neutral atom has 99 protons and 99 electrons.

What is the chemical symbol for Einsteinium?

The chemical symbol for Einsteinium is Es.

What category is Einsteinium in?

Einsteinium is classified as a actinide and sits in period 7 of the periodic table.

Element 99

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

Period

Group

Actinide series

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

Why Einsteinium Matters

Einsteinium helps connect atomic number 99, actinide behavior, period 7 trends, and electron shell structure. Its solid phase, atomic mass of 252 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹¹ make it useful for comparing bonding patterns across the periodic table.

Discovery and Occurrence

Einsteinium was discovered 1952 by Albert Ghiorso, Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey. 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.

Safety and Handling Context

Einsteinium has radioactive isotopes or is commonly discussed with radioactive materials. Use this page as an educational reference; real samples require qualified supervision and controlled handling.

Related Elements

Frequently Asked Questions

What is the atomic number of Einsteinium?: Einsteinium has atomic number 99, which means a neutral atom has 99 protons and 99 electrons.
What is the chemical symbol for Einsteinium?: The chemical symbol for Einsteinium is Es.
What category is Einsteinium in?: Einsteinium is classified as a actinide and sits in period 7 of the periodic table.

Explore Einsteinium in 3D

Use the interactive table above to rotate atomic models, compare periodic trends, and move from Einsteinium to neighboring elements without losing your place.