Atomic Number
85
Element 85
Astatine (At)
Astatine is a chemical element with symbol At and atomic number 85. It is the rarest naturally occurring element in the Earth's crust, occurring only as the decay product of various heavier elements.
Atomic Mass
210 u
Category
Halogen
Period
6
Group
Group 17: halogens
Phase
solid
Density
7 g/cm3
Electron Shells
2, 8, 18, 32, 18, 7
Atomic Structure
Protons: 85. Electrons: 85. Neutrons: Varies by isotope.
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁵
Why Astatine Matters
Astatine helps connect atomic number 85, halogen behavior, period 6 trends, and electron shell structure. Its solid phase, atomic mass of 210 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁵ make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Astatine was discovered 1940 by Dale R. Corson, Kenneth Ross MacKenzie, Emilio Segrè. Astatine is a chemical element with symbol At and atomic number 85. It is the rarest naturally occurring element in the Earth's crust, occurring only as the decay product of various heavier elements.
Safety and Handling Context
Astatine 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 Astatine?
- Astatine has atomic number 85, which means a neutral atom has 85 protons and 85 electrons.
- What is the chemical symbol for Astatine?
- The chemical symbol for Astatine is At.
- What category is Astatine in?
- Astatine is classified as a halogen and sits in period 6 of the periodic table.
Explore Astatine in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Astatine to neighboring elements without losing your place.