Element / isotope identity
Francium isotope decay is experimentally established.
Tracer chemistry
Trace chemistry supports +1 alkali behavior.
Phase estimates
Displayed phase boundaries are literature estimates.
Bulk density / crystal
No macroscopic density or crystal lattice is measured.
Safety boundary
No production, trapping, separation or handling instructions.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Francium (Fr)
Francium is element 87, the heaviest naturally occurring alkali metal and one of the rarest naturally occurring elements. Its 7s¹ configuration supports +1 chemistry, but no macroscopic francium sample exists to establish ordinary bulk structure or appearance.
Francium atomic number, mass, electron configuration and key properties
Francium: quick answers
How many protons, neutrons and electrons does francium have?
Francium’s atomic number is 87, so every francium atom has 87 protons, and a neutral atom also has 87 electrons. Francium has no stable isotopes, so the neutron count depends on the isotope: francium-223, featured on this page, has 136 neutrons.
What is the symbol for francium?
The chemical symbol for francium is Fr.
Is francium a solid, liquid or gas at room temperature?
Francium has never been collected in a visible amount, so its state has not been observed; it is predicted to be a liquid or very soft solid near room temperature.
What family (group) is francium in?
Francium is an alkali metal, in group 1, period 7 of the periodic table.
How many valence electrons does francium have?
Francium has 1 valence electron, the single electron in its outer shell, which matches its position in group 1.
What is the electron configuration of francium?
The ground-state electron configuration of francium is [Rn] 7s¹.
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.
87 protons define francium.
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.
Francium in its period and family
Francium is the Period 7 Group 1 element below cesium. Its 7s¹ valence pattern strongly suggests alkali-metal +1 chemistry, while relativistic effects and extreme scarcity limit direct bulk measurements.
Francium Visual Lab
Toggle the neutral 7s¹ atom to the Fr⁺ electron-count teaching state, rotate a ²²³Fr nucleus, and use the Evidence Lens to separate tracer-scale chemistry from estimated phase properties 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.
Francium in one minute
Atomic number 87 means 87 protons.
The reference configuration is [Rn] 7s¹.
²²³Fr has a half-life of only about 22 minutes, so francium never accumulates in macroscopic natural samples.
Francium commonly behaves as a +1 alkali-metal ion in tracer chemistry.
Bulk density and crystal structure are not measured.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 18 · 32 · 18 · 8 · 1 electrons
The 7s cloud is an isolated-atom nonrelativistic teaching model. Heavy-atom relativistic effects are important and the visual is not a measured bulk-electron distribution.
Francium exists atom-at-a-time or in tiny transient quantities. A bulk alkali-metal lattice has not been measured, so the material viewer does not copy a cesium-like crystal as if it were experimental fact.. 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 7s cloud is an isolated-atom nonrelativistic teaching model. Heavy-atom relativistic effects are important and the visual is not a measured bulk-electron distribution.
Where do I meet francium?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Natural decay chain
Francium appears transiently in the actinium decay series and disappears through radioactive decay.
Transient natural atom → +1 tracer chemistry → unknown bulk metal
Francium looks simple in the periodic table but difficult in the laboratory: its nuclear lifetime prevents ordinary bulk measurements.
²²³Fr decay
Short-lived francium isotopes and decay behavior are experimental.
Rubidium, cesium and francium
The ns¹ pattern continues while experimental access collapses at short-lived francium.
| Evidence | bulk measured |
|---|---|
| Outer | 5s¹ |
| Evidence | bulk measured |
|---|---|
| Outer | 6s¹ |
| Evidence | tracer / predicted bulk |
|---|---|
| Outer | 7s¹ |
Francium 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 | 87 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | [223] | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Rn] 7s¹ | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group 1 · Period 7 · s-block | Periodic-table placement | Evaluated |
| Electronegativity | ≈0.7 (estimate) | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ²²³Fr | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Expected alkali-metal condensed state near room temperature; no macroscopic sample exists | Source-reviewed; see Sources below | Predicted |
| Density | Unknown | Source-reviewed; see Sources below | Unknown |
| Material / molecular structure | No measured macroscopic crystal structure | Francium exists atom-at-a-time or in tiny transient quantities. A bulk alkali-metal lattice has not been measured, so the material viewer does not copy a cesium-like crystal as if it were experimental fact. | Measured |
| Classification | Radioactive alkali metal · evidence-limited bulk element | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Francium exists atom-at-a-time or in tiny transient quantities. A bulk alkali-metal lattice has not been measured, so the material viewer does not copy a cesium-like crystal as if it were experimental fact. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | Estimated ≈294 K | Source-reviewed; see Sources below | Predicted |
| Boiling / gas reference | Estimated ≈923 K | Source-reviewed; see Sources below | Predicted |
| Phase-path context | Francium has no measured macroscopic phase diagram. Estimated boundaries near 294 K and 923 K may be shown only as predicted teaching references, not as ordinary measured bulk constants. | 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 expected and chemically supported at tracer scale | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | Fr⁺ | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Francium is the Period 7 Group 1 element below cesium. Its 7s¹ valence pattern strongly suggests alkali-metal +1 chemistry, while relativistic effects and extreme scarcity limit direct bulk measurements. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ²²³Fr | Radioactive natural isotope | Reference teaching nucleus with 87 protons and 136 neutrons; half-life about 22 minutes. | Evaluated |
| ²²¹Fr | Radioactive isotope | Another short-lived francium isotope. | Evaluated |
| Francium isotope context | No stable isotopes | All known francium isotopes are radioactive. | Evaluated |
| Teaching nucleus | ²²³Fr · 87 protons + 136 neutrons | Reference isotope used in the nucleus model | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Page evidence note | Atomic number, isotope identities and tracer chemistry are measured/evaluated. Bulk density and crystal structure are unknown. Melting/boiling values are literature estimates and remain visibly predicted. | Evidence summary for this guide | Reviewed |
| Structure evidence | Francium exists atom-at-a-time or in tiny transient quantities. A bulk alkali-metal lattice has not been measured, so the material viewer does not copy a cesium-like crystal as if it were experimental fact. | 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 Francium a solid, liquid or gas? State at temperature
Francium has no measured macroscopic phase diagram. Estimated boundaries near 294 K and 923 K may be shown only as predicted teaching references, not as ordinary measured bulk constants.
Where on Earth is Francium found or produced?
Who discovered Francium, and when?
Marguerite Perey discovered francium while studying actinium decay at the Curie Institute in Paris.
Tracer chemistry established alkali-metal-like behavior.
Small numbers of francium atoms have been used in specialized atomic-physics experiments.
No macroscopic sample has been available for ordinary bulk property measurements.
How francium is observed: natural decay and atom-scale research
Francium appears transiently in natural decay chains; it does not form mineable deposits.
Radioactive decay measurements establish isotope identity and nuclear behavior.
Tracer-scale chemistry tests ionic behavior without accumulating bulk material.
Specialized research may create or trap small numbers of atoms; this guide gives no production or apparatus settings.
What is francium used for?
Fundamental atomic physics
Francium provides a heavy alkali atom for precision and symmetry studies.
Nuclear/decay research
Its isotopes contribute to decay-chain science.
Periodic-trend testing
Francium challenges simple extrapolation of Group 1 properties into a relativistic heavy-atom regime.
No practical bulk use
Its scarcity and short half-lives prevent conventional industrial applications.
Francium isotopes and natural abundance
²²³Fr
Radioactive natural isotopeReference teaching nucleus with 87 protons and 136 neutrons; half-life about 22 minutes.
²²¹Fr
Radioactive isotopeAnother short-lived francium isotope.
Francium isotope context
No stable isotopesAll known francium isotopes are radioactive.
Five-question Francium check
What is francium’s atomic number?
What is the reference outer configuration?
What is the measured bulk crystal structure?
Who discovered francium?
Why is there no practical bulk use?
Francium 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 francium?
Short answer: Francium is element 87, a radioactive Group 1 element.
Atomic number 87 means every francium nucleus contains 87 protons. In the periodic table, Francium is classified here as a radioactive alkali metal · evidence-limited bulk element in Period 7 and Group 1. Francium is the Period 7 Group 1 element below cesium. Its 7s¹ valence pattern strongly suggests alkali-metal +1 chemistry, while relativistic effects and extreme scarcity limit direct bulk measurements.
Key point: Fr is element 87; its periodic position and electron structure explain the rest of the page.
What is francium used for?
Short answer: Fundamental atomic and nuclear research; it has no practical bulk use.
Fundamental atomic physics: Francium provides a heavy alkali atom for precision and symmetry studies. Nuclear/decay research: Its isotopes contribute to decay-chain science. The periodic table predicts a strong family resemblance to cesium, but family resemblance is not measurement. Francium’s bulk state, density and crystal structure must remain evidence-limited.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
Is francium a metal?
Short answer: It is classified as an alkali metal by periodic position and tracer chemistry, but macroscopic metallic properties cannot be measured from a bulk sample.
This guide classifies Francium as a radioactive alkali metal · evidence-limited bulk element. Its periodic position is Period 7, s-block, Group 1. Francium is the Period 7 Group 1 element below cesium. Its 7s¹ valence pattern strongly suggests alkali-metal +1 chemistry, while relativistic effects and extreme scarcity limit direct bulk measurements.
Key point: Periodic-table classification describes recurring atomic/chemical behavior; it does not make every element in a column physically identical.
Where is francium found?
Short answer: Only transiently in natural radioactive decay chains and in specialized research.
Francium appears transiently in natural decay chains; it does not form mineable deposits. The Geography Explorer keeps natural occurrence separate from resources, industrial production and recycling, because those datasets answer different questions about francium.
Key point: Natural occurrence, resources, production and recycling are different geography questions.
Where was francium discovered?
Short answer: At the Curie Institute in Paris by Marguerite Perey in 1939.
In 1939, Marguerite Perey discovered francium while studying actinium decay at the Curie Institute in Paris. In the 20th century, Tracer chemistry established alkali-metal-like behavior.
Key point: Discovery location/history is different from natural occurrence or modern production geography.
How many valence electrons does francium have?
Short answer: One in the reference 7s¹ configuration.
The neutral-atom ground-state reference used on this page is [Rn] 7s¹. This is an isolated-atom reference: bonding and ion formation can change which outer electrons are present or chemically active. The listed common oxidation-state context is +1 expected and chemically supported at tracer scale, which helps connect the atomic configuration to ordinary chemistry without treating electron counting as a single universal rule.
Key point: Electron configuration is a ground-state atomic reference, not a literal picture of every compound.
Scientific sources for Francium
Questions to ask next about Francium
A good element lesson should lead to the next useful question, not end after a list of facts.
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