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85 At Astatine 210

Astatine

METALLOID
Bohr Model: Electrons arranged in energy shells around the nucleus.

Astatine is a very rare radioactive chemical element with the chemical symbol At and atomic number 85. It occurs on Earth as the decay product of various heavier elements. All its isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours.

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Quick Facts

Atomic Number 85
Period 6
Group 17
Phase Solid
Appearance unknown, probably metallic
About Metalloids

Metalloids have properties intermediate between metals and nonmetals. They often act as semi-conductors, making them essential for electronics.

History

Discovered By Dale R. Corson
Named By Unknown

Physical Properties

Atomic Mass 210
Density 6.35 g/L
Molar Heat N/A J/(mol·K)
Phase Transition (Melting & Boiling Points)

Astatine melts at 575 K and boils at 610 K.

Atomic Properties

Electron Config [Xe] 4f14 5d10 6s2 6p5
Electronegativity 2.2
Electron Affinity 233 kJ/mol
Ionization Energy 899.003 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

Image of Astatine Source: Wikipedia

External Resources

Wikipedia PubChem Royal Society of Chemistry Periodic Videos (YouTube)

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.