francium
Let an agent explain francium as an element, relay its properties, occurrence and research uses from reference sources, and separate fact from popular exaggeration about its reactivity and quantity.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify
Researched by: Claude
Purpose and description
Let an agent explain francium as an element, relay its properties, occurrence and research uses from reference sources, and separate fact from popular exaggeration about its reactivity and quantity.
A highly radioactive alkali metal, chemical element 87, the heaviest member of group 1 and one of the rarest naturally occurring elements, formed in trace amounts by decay of actinium; its longest-lived isotope, francium-223, has a half-life of about 22 minutes, so it has no practical uses beyond research in atomic physics and spectroscopy.
What it is for: Not for anything practical; a subject of atomic research.
It can be explain properties and isotopes; explain occurrence and how it is made; relay research uses; correct common exaggerations.
Distinguishing features
Heaviest alkali metal
No stable isotopes
Trace natural occurrence in uranium ores
Studied as trapped atoms
What it looks like
Never seen in bulk; expected to be a silvery metal, observed only as trapped atoms.
Physical character
atomic number: 87
half-life of francium-223: about 22 minutes - longest-lived isotope
natural abundance: grams at any time in the crust estimate - often quoted as about 20-30 g
How it is recognised
Element 87, alkali metal
Extremely radioactive and short-lived
Caesium is the heaviest stable alkali metal
Related models
is a kind of - group 1
is produced by - decay of actinium-227
is related to - the lighter homologue
is studied in - trapped atom experiments
In practice
Families and kinds
francium-223 from actinium decay
synthetic isotopes made in accelerators
francium in atomic physics experiments
Identifiers
chemical symbol Fr
CAS number 7440-73-5
Standards and regulation
Radiation protection regulations for research handling
Failure modes and hazards
Radiation hazard in research
Popular claims about explosive reactivity that cannot be tested in bulk
Confusing estimates of natural quantity
Also called
+8
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.francium
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Element What francium is.
Chemistry.
Properties
Properties and isotopes.
Properties
Properties.
- What are the known and predicted properties of francium, and what isotopes exist? definition
- Is the question about the element or about popular claims that need correction? boundary
Occurrence
Occurrence and production.
Occurrence
Occurrence.
- How does francium occur naturally, and how is it produced for research? provenance
- Which entry fits actinium? action
Research Scientific use.
Research.
Experiments
Trapped atom experiments.
Experiments
Experiments.
- How is francium studied in atom traps, and what questions do experiments address? provenance
- Which references are standard? provenance
Limits
What cannot be done.
Limits
Limits.
- Why can francium not be studied in bulk, and what follows for claims about it? provenance
- Which entry fits radioactive decay? action
Safety Radiation.
Safety.
Radiation
Radiation hazard.
Radiation
Radiation.
- What radiation protection rules apply to research with francium? provenance
- Which entry fits radiation protection? action
Handling
Handling.
Handling
Handling.
- How are trace amounts handled in laboratories? provenance
- Is the question about a specific facility, which needs its safety officer? boundary
Context History and teaching.
Context.
History
Discovery.
History
History.
- How did Marguerite Perey discover francium in 1939? provenance
- Which entry fits the discoverer? action
Teach
Teaching.
Teach
Teaching.
- How is francium presented in teaching, and which misconceptions arise? provenance
- Which entry fits the periodic table? action
What the second pass must settle
- Should isotopes be separate entries?
- How should research references be linked?
- The registry entry has merged isotope aliases; should they be split off?