Element / isotope identity
Production/decay establishes astatine isotope identities.
Tracer chemistry
Selected chemistry is supported by tiny-quantity experiments.
Phase estimates
Displayed ~573 K/~623 K values are estimates, not measured bulk transitions.
Bulk density / crystal
No measured macroscopic density or crystal lattice is asserted.
Safety boundary
No production, separation, dose or handling instructions.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Astatine (At)
Astatine is element 85, an extremely rare radioactive halogen. Its nuclear identity and selected atom-scale chemistry are experimental, but macroscopic density, crystal structure and ordinary bulk appearance are not measured facts.
Astatine atomic number, mass, electron configuration and key properties
Astatine: quick answers
How many protons, neutrons and electrons does astatine have?
Astatine’s atomic number is 85, so every astatine atom has 85 protons, and a neutral atom also has 85 electrons. Astatine has no stable isotopes, so the neutron count depends on the isotope: astatine-211, featured on this page, has 126 neutrons.
What is the symbol for astatine?
The chemical symbol for astatine is At.
Is astatine a solid, liquid or gas at room temperature?
Astatine has never been collected in a visible amount, so its state has not been observed; it is predicted to be a solid.
What family (group) is astatine in?
Astatine is a halogen, in group 17, period 6 of the periodic table.
How many valence electrons does astatine have?
Astatine has 7 valence electrons, the electrons in its outer shell, which matches its position in group 17.
What is the electron configuration of astatine?
The ground-state electron configuration of astatine is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵.
From atomic number to chemistry
Read these as a chain of causes, not as isolated facts. Each step links to the concept hub if you want the underlying idea explained.
85 protons define astatine.
The reference ground-state configuration frames atomic and chemical behavior.
Periodic position organizes recurring trends without replacing element-specific evidence.
The teaching nucleus is one isotope, not the relative atomic mass.
Phase claims preserve measured/evaluated/predicted/unknown evidence labels.
Astatine in its period and family
Astatine is the Period 6 Group 17 element below iodine. Halogen trends guide chemistry expectations, but strong relativistic effects and tiny atom counts make simple extrapolation unreliable.
Astatine Visual Lab
Rotate a ²¹¹At teaching nucleus and 6s/6p probability models, then use the Evidence Lens to separate measured decay/chemistry from estimated phase boundaries and unknown bulk structure.
Every mark points to one exact feature
The numbered markers explain the same information system used throughout Element Lookup. Unknown or predicted fields remain visibly labelled rather than being replaced with guesses.
Astatine in one minute
Atomic number 85 means 85 protons.
Astatine has no stable isotopes and exists only in tiny transient quantities.
²¹¹At is an important research isotope in targeted-alpha therapy studies.
Bulk density and crystal structure are not measured.
Estimated melting/boiling values must remain labeled estimates rather than measurements.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 18 · 32 · 18 · 7 electrons
The 6s/6p clouds are nonrelativistic teaching shapes tied to the reference configuration. Superheavy/very-heavy atomic chemistry requires relativistic treatment beyond this visual.
Only extremely small quantities of astatine have been produced or occur transiently. No measured bulk crystal lattice is rendered; the Structure panel is an evidence panel rather than an invented halogen lattice.. The viewer is evidence-aware: measured structures are identified as such; unknown bulk structures stay unknown.
Teaching visualization; not a literal finite sample or thermal trajectory.What this model does—and does not—show
The 6s/6p clouds are nonrelativistic teaching shapes tied to the reference configuration. Superheavy/very-heavy atomic chemistry requires relativistic treatment beyond this visual.
Where do I meet astatine?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Natural trace occurrence
Astatine appears only fleetingly in natural radioactive decay chains; there is no mineable astatine resource.
Measured nucleus → sparse chemistry → estimated phases → unknown bulk
Astatine is an evidence hierarchy: some nuclear and tracer facts are measured, while macroscopic material properties are not.
Decay + isotope identity
Astatine isotope production and radioactive decay are experimental.
Iodine, astatine and tennessine
Moving into the heaviest halogens changes not only chemistry but also how much evidence is experimentally accessible.
| Evidence | bulk measured |
|---|---|
| Form | I₂ molecular solid |
| Evidence | trace chemistry |
|---|---|
| Bulk | unknown / estimated |
| Evidence | atom-scale + predicted |
|---|---|
| Bulk | unknown |
Astatine properties: atomic, physical, thermal and chemical
Categories follow the science of this element rather than a fixed decorative template. Each row carries condition/provenance context and an evidence label; unknown values stay unknown.
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Atomic number | 85 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | [210] | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵ | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group 17 · Period 6 · p-block | Periodic-table placement | Evaluated |
| Electronegativity | ≈2.2 (estimate) | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ²¹¹At | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Expected condensed element near room temperature; no macroscopic sample has been measured | Source-reviewed; see Sources below | Predicted |
| Density | Unknown | Source-reviewed; see Sources below | Unknown |
| Material / molecular structure | No measured macroscopic crystal structure | Only extremely small quantities of astatine have been produced or occur transiently. No measured bulk crystal lattice is rendered; the Structure panel is an evidence panel rather than an invented halogen lattice. | Measured |
| Classification | Radioactive halogen · evidence-limited bulk element | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Only extremely small quantities of astatine have been produced or occur transiently. No measured bulk crystal lattice is rendered; the Structure panel is an evidence panel rather than an invented halogen lattice. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | Estimated ≈573 K | Source-reviewed; see Sources below | Predicted |
| Boiling / gas reference | Estimated ≈623 K | Source-reviewed; see Sources below | Predicted |
| Phase-path context | No measured macroscopic astatine phase diagram exists. The teaching slider may show literature estimates near 573 K and 623 K, but every boundary is explicitly predicted/estimated rather than measured. | Shared phase registry drives the slider, regions and markers. | Evaluated |
| Condition warning | Temperature and pressure define phase behavior; purity/allotropy may matter. | Teaching condition statement | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Common oxidation states | −1, +1, +3, +5, +7 reported/predicted in sparse chemistry | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | Element-specific; see chemistry sections | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Astatine is the Period 6 Group 17 element below iodine. Halogen trends guide chemistry expectations, but strong relativistic effects and tiny atom counts make simple extrapolation unreliable. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ²¹¹At | Radioactive isotope · research-important | Reference teaching nucleus with 85 protons and 126 neutrons. | Evaluated |
| ²¹⁰At | Radioactive isotope | One of several short-lived astatine isotopes. | Evaluated |
| Astatine isotope context | No stable isotopes | All known astatine isotopes are radioactive. | Evaluated |
| Teaching nucleus | ²¹¹At · 85 protons + 126 neutrons | Reference isotope used in the nucleus model | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Page evidence note | Atomic number, isotope identity and decay are experimental/evaluated. Selected tracer chemistry is experimental. Density and crystal structure are unknown; displayed phase temperatures are estimates and are labelled predicted. | Evidence summary for this guide | Reviewed |
| Structure evidence | Only extremely small quantities of astatine have been produced or occur transiently. No measured bulk crystal lattice is rendered; the Structure panel is an evidence panel rather than an invented halogen lattice. | Measured structure, labelled schematic, prediction or explicit unknown as applicable. | Reviewed |
| Map evidence rule | Real pins are reviewed examples; conceptual layers are used when pins would mislead. | Geography Explorer 2.0 | Reviewed |
| Source set | 2 primary/reference links listed below | Open the Sources section for the actual references. | Reviewed |
Is Astatine a solid, liquid or gas? State at temperature
No measured macroscopic astatine phase diagram exists. The teaching slider may show literature estimates near 573 K and 623 K, but every boundary is explicitly predicted/estimated rather than measured.
Where on Earth is Astatine found or produced?
Who discovered Astatine, and when?
Corson, MacKenzie and Segrè produced astatine at the University of California, Berkeley.
Tracer-scale chemistry established several halogen-like behaviors.
²¹¹At is studied in targeted-alpha radionuclide therapy research.
Because quantities are minute and short-lived, many bulk properties remain estimated or unknown.
How astatine knowledge is built: trace atoms, decay and chemistry
Natural astatine exists only transiently in radioactive decay chains and never accumulates as a resource.
Research produces tiny amounts for nuclear/chemical study; this guide gives no production settings or separation procedures.
Decay measurements establish isotope identity and half-life information.
Chemical experiments and theory constrain behavior, while unmeasured bulk properties remain explicitly unknown.
What is astatine used for?
Fundamental research
Astatine tests heavy-halogen and relativistic chemistry.
Targeted-alpha research
²¹¹At is investigated in controlled radiopharmaceutical research.
No bulk commercial use
Astatine’s scarcity and short-lived isotopes prevent ordinary macroscopic industrial use.
Evidence education
The element is a strong example of separating measured atom-scale facts from predicted bulk behavior.
Astatine isotopes and natural abundance
²¹¹At
Radioactive isotope · research-importantReference teaching nucleus with 85 protons and 126 neutrons.
²¹⁰At
Radioactive isotopeOne of several short-lived astatine isotopes.
Astatine isotope context
No stable isotopesAll known astatine isotopes are radioactive.
Five-question Astatine check
What is astatine’s atomic number?
What is its measured macroscopic density?
How should the ~573 K melting value be labelled?
Which isotope is important in targeted-alpha research?
What should the material viewer do?
Astatine questions students commonly ask
Each answer starts with the direct fact, then explains the chemistry, evidence or material context so the result is understandable rather than merely memorized.
What is astatine?
Short answer: Astatine is element 85, a rare radioactive member of Group 17.
Atomic number 85 means every astatine nucleus contains 85 protons. In the periodic table, Astatine is classified here as a radioactive halogen · evidence-limited bulk element in Period 6 and Group 17. Astatine is the Period 6 Group 17 element below iodine. Halogen trends guide chemistry expectations, but strong relativistic effects and tiny atom counts make simple extrapolation unreliable.
Key point: At is element 85; its periodic position and electron structure explain the rest of the page.
Is astatine a metal, nonmetal, or metalloid?
Short answer: Astatine is unambiguously a Group 17 halogen, but assigning a bulk “metal/nonmetal/metalloid” label is much less secure because macroscopic astatine has never been available for direct property measurements.
Only trace atom-scale quantities of astatine can be produced or observed before radioactive decay removes them. Its chemistry confirms a strong halogen relationship, while relativistic calculations and limited experiments also suggest behavior that becomes less nonmetal-like down Group 17. That is not the same as a measured bulk classification. A careful answer therefore separates the well-supported periodic classification (halogen) from an evidence-limited classroom label (metal/nonmetal/metalloid).
Key point: Call astatine a halogen first; treat a metalloid/metal/nonmetal label as model-dependent and evidence-limited, not as a directly measured bulk fact.
What is astatine used for?
Short answer: Fundamental research and ²¹¹At targeted-alpha therapy research; there is no bulk commercial use.
Fundamental research: Astatine tests heavy-halogen and relativistic chemistry. Targeted-alpha research: ²¹¹At is investigated in controlled radiopharmaceutical research. Astatine is where an Evidence Lens matters more than a glossy periodic-table square. Search queries asking what it “looks like” should be answered with the limitation: no macroscopic sample has established a bulk appearance.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
What does astatine look like?
Short answer: No experimentally established macroscopic appearance exists because macroscopic samples have not been measured.
The ordinary elemental-material description used here is: Expected condensed element near room temperature; no macroscopic sample has been measured. Astatine is where an Evidence Lens matters more than a glossy periodic-table square. Search queries asking what it “looks like” should be answered with the limitation: no macroscopic sample has established a bulk appearance.
Key point: Elemental appearance can differ from the colors of its ions, compounds, oxide films or host materials.
Is astatine a metal?
Short answer: It is a Group 17 element with predicted mixed/metallic tendencies; a normal bulk-metal classification is not directly established by a macroscopic sample.
This guide classifies Astatine as a radioactive halogen · evidence-limited bulk element. Its periodic position is Period 6, p-block, Group 17. Astatine is the Period 6 Group 17 element below iodine. Halogen trends guide chemistry expectations, but strong relativistic effects and tiny atom counts make simple extrapolation unreliable.
Key point: Periodic-table classification describes recurring atomic/chemical behavior; it does not make every element in a column physically identical.
Who discovered astatine?
Short answer: Dale Corson, Kenneth MacKenzie and Emilio Segrè in 1940.
In 1940, Corson, MacKenzie and Segrè produced astatine at the University of California, Berkeley. In the mid-20th century, Tracer-scale chemistry established several halogen-like behaviors.
Key point: Discovery credit follows the historical evidence and accepted attribution, not just the earliest claim.
Scientific sources for Astatine
Questions to ask next about Astatine
A good element lesson should lead to the next useful question, not end after a list of facts.
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