Element identity
Atomic number, periodic identity and reference mass/isotope conventions are established and source-reviewed.
Atomic / electronic model
Atomic configurations and orbital teaching models are reference interpretations; heavy-element electronic structure is more complex than a classical shell picture.
Nuclear / isotope data
Half-lives, isotope identities and decay information are taken from evaluated nuclear-data/reference sources and remain isotope-specific.
Material / phase data
Ordinary bulk and phase values are shown only where defensible; solid-state transitions are kept separate from melting.
Geography / safety boundary
Occurrence, discovery and public research context may be mapped. Operational radioactive-material inventories, access routes and sensitive facility details are intentionally not mapped.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Radium (Ra)
Radium is element 88, a highly radioactive Group 2 metal discovered by Marie and Pierre Curie in 1898. It occurs naturally in uranium decay chains in trace amounts, and its isotopes connect chemistry to radioactivity, environmental monitoring and carefully controlled medical use.
Radium atomic number, mass, electron configuration and key properties
Radium: quick answers
How many protons, neutrons and electrons does radium have?
Radium’s atomic number is 88, so every radium atom has 88 protons, and a neutral atom also has 88 electrons. Radium has no stable isotopes, so the number of neutrons depends on which isotope you mean.
What is the symbol for radium?
The chemical symbol for radium is Ra.
Is radium a solid, liquid or gas at room temperature?
Radium is a solid at room temperature (about 25 °C).
What family (group) is radium in?
Radium is an alkaline earth metal, in group 2, period 7 of the periodic table.
How many valence electrons does radium have?
Radium has 2 valence electrons, the electrons in its outer shell, which matches its position in group 2.
What is the electron configuration of radium?
The ground-state electron configuration of radium is [Rn] 7s².
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.
Eighty-eight protons define radium; every isotope shares that proton count.
Two outer 7s electrons connect radium to Group 2 +2 chemistry.
Radium is the heaviest alkaline-earth element.
Radium isotope identity and half-life are essential, not optional details.
Chemical +2 behavior and nuclear decay must be explained separately.
Radium in its period and family
Radium sits at the bottom of Group 2 below barium. Its two outer 7s electrons support alkaline-earth +2 chemistry, but nuclear decay and isotope half-life are essential parts of any scientifically honest radium description.
Radium Visual Lab
Decode radium’s tile, rotate a ²²⁶Ra teaching nucleus and reported BCC metal cell, inspect 7s and representative 6p core probability models, then connect radium to decay chains, discovery history, environmental monitoring and Ra-223 medicine.
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.
Radium in one minute
Atomic number 88 means every radium nucleus contains 88 protons.
The ground-state reference configuration is [Rn] 7s² and +2 is the characteristic oxidation state.
All radium isotopes are radioactive; ²²⁶Ra is a key long-lived natural isotope.
Radium occurs only in trace quantities as part of uranium/thorium decay series, not as large native-metal deposits.
Radium-223 has a regulated medical role in certain prostate-cancer settings involving bone metastases.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 18 · 32 · 18 · 8 · 2 electrons
The 7s view represents the occupied outer s orbital in a nonrelativistic hydrogen-like teaching approximation; 6p is an occupied core-region representative. For Z = 88, relativistic and many-electron effects matter, so the page labels these as qualitative orbital-shape models rather than scale-accurate electron densities.
Body-centred cubic radium metal is commonly reported; bulk data are limited because radium is highly radioactive and scarce. 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 view represents the occupied outer s orbital in a nonrelativistic hydrogen-like teaching approximation; 6p is an occupied core-region representative. For Z = 88, relativistic and many-electron effects matter, so the page labels these as qualitative orbital-shape models rather than scale-accurate electron densities.
Where do I meet radium?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Decay chains
Natural radium isotopes appear as daughter products in uranium/thorium radioactive decay series and occur only in trace concentrations.
From decay-series daughter to regulated medical isotope
Radium’s modern story is nuclear and historical; safe context matters as much as the numbers.
Decay-series trace
Natural radium appears as a daughter in uranium/thorium decay chains and can enter rocks or groundwater.
Calcium, barium and radium
Group 2 shares an ns² outer-shell pattern and characteristic +2 chemistry. Radium continues that chemistry while radioactivity becomes the dominant practical distinction.
| Valence | 4s² |
|---|---|
| Common ion | Ca²⁺ |
| Valence | 6s² |
|---|---|
| Common ion | Ba²⁺ |
| Valence | 7s² |
|---|---|
| Common ion | Ra²⁺ |
| Nuclear | all isotopes radioactive |
Radium 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 | 88 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | [226] | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Rn] 7s² | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group 2 · Period 7 · s-block | Periodic-table placement | Evaluated |
| Electronegativity | ≈0.9 (context-dependent) | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ²²⁶Ra | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Radioactive solid metal | Source-reviewed; see Sources below | Evaluated |
| Density | ≈5 g/cm³ | Source-reviewed; see Sources below | Predicted |
| Material / molecular structure | BCC (reported) | Body-centred cubic radium metal is commonly reported; bulk data are limited because radium is highly radioactive and scarce | Measured |
| Classification | Radioactive alkaline-earth metal | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | Body-centred cubic radium metal is commonly reported; bulk data are limited because radium is highly radioactive and scarce | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 969 K | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | 1773 K | Source-reviewed; see Sources below | Evaluated |
| Phase-path context | A simplified approximately standard-pressure path uses 969 K as the melting reference and 1773 K as the boiling reference. These bulk values are far less experimentally routine than data for common stable metals. | 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 | +2 | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | Ra²⁺ | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Radium sits at the bottom of Group 2 below barium. Its two outer 7s electrons support alkaline-earth +2 chemistry, but nuclear decay and isotope half-life are essential parts of any scientifically honest radium description. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ²²⁶Ra | Radioactive · half-life ≈1600 years | A major natural radium isotope in the ²³⁸U decay series and a key environmental-radiological reference. | Evaluated |
| ²²³Ra | Radioactive · half-life ≈11.4 days | An alpha-emitting isotope used as radium-223 dichloride in specific regulated cancer therapy. | Evaluated |
| ²²⁴Ra | Radioactive · half-life ≈3.66 days | A naturally occurring radium isotope in the thorium decay series. | Evaluated |
| Teaching nucleus | ²²⁶Ra · 88 protons + 138 neutrons | Reference isotope used in the nucleus model | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Page evidence note | All radium isotopes are radioactive. Atomic/nuclear values are source-reviewed, while scarce bulk-metal properties carry more uncertainty than common stable metals. Medical statements are descriptive, not treatment advice. | Evidence summary for this guide | Reviewed |
| Structure evidence | Body-centred cubic radium metal is commonly reported; bulk data are limited because radium is highly radioactive and scarce | 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 | 4 primary/reference links listed below | Open the Sources section for the actual references. | Reviewed |
Is Radium a solid, liquid or gas? State at temperature
A simplified approximately standard-pressure path uses 969 K as the melting reference and 1773 K as the boiling reference. These bulk values are far less experimentally routine than data for common stable metals.
Where on Earth is Radium found or produced?
Who discovered Radium, and when?
Marie Curie and Pierre Curie announced radium after studying highly radioactive pitchblende residues.
Marie Curie and André Debierne isolated radium metal through specialized laboratory work.
Radium entered medicine and luminous paints before its hazards were adequately understood.
Modern use is limited and tightly controlled; Ra-223 has a specific role as a radiopharmaceutical in certain cancer care.
How radium enters science, environment and medicine - conceptual only
Natural radium forms in radioactive decay series associated with uranium and thorium.
Environmental science measures trace radium in rocks, soils and waters to understand exposure and geochemistry.
Historical isolation required extensive radiochemical separation, but Element Lookup does not reproduce operational separation procedures.
Modern medical radium-223 is manufactured and administered within regulated radiopharmaceutical systems; this page stays at the conceptual science level.
What is radium used for?
Radium-223 medicine
Ra-223 dichloride is used in specific cases of prostate cancer metastatic to bone, under specialist clinical care.
Scientific history
Radium was central to early radioactivity research and helped transform understanding of atoms and nuclei.
Environmental tracing/monitoring
Radium isotopes can be measured in hydrogeology and environmental radioactivity studies.
Historical luminous paint
Former luminous-paint use is now primarily a radiation-safety and occupational-health lesson.
Radium isotopes and natural abundance
²²⁶Ra
Radioactive · half-life ≈1600 yearsA major natural radium isotope in the ²³⁸U decay series and a key environmental-radiological reference.
²²³Ra
Radioactive · half-life ≈11.4 daysAn alpha-emitting isotope used as radium-223 dichloride in specific regulated cancer therapy.
²²⁴Ra
Radioactive · half-life ≈3.66 daysA naturally occurring radium isotope in the thorium decay series.
Five-question Radium check
What is radium’s atomic number?
Does radium have stable isotopes?
Which oxidation state is characteristic for radium chemistry?
Which radium isotope has a modern regulated medical use?
Why is a “radium mine-production map” misleading?
Radium 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 radium?
Short answer: Radium is chemical element 88, a highly radioactive alkaline-earth metal in Group 2.
Atomic number 88 means every radium nucleus contains 88 protons. In the periodic table, Radium is classified here as a radioactive alkaline-earth metal in Period 7 and Group 2. Radium sits at the bottom of Group 2 below barium. Its two outer 7s electrons support alkaline-earth +2 chemistry, but nuclear decay and isotope half-life are essential parts of any scientifically honest radium description.
Key point: Ra is element 88; its periodic position and electron structure explain the rest of the page.
Why is radium dangerous?
Short answer: Radium is radioactive, and internalized radium can be especially hazardous because Ra²⁺ behaves chemically somewhat like Ca²⁺ and can be incorporated into bone, exposing nearby tissue as it decays.
The hazard is not just the word “radioactive.” It depends on isotope, activity, exposure route and where the material goes in the body. Radium decay can also produce radon, adding a decay-chain dimension. Historical luminous-paint exposures demonstrated why persistent internal deposition of alpha-emitting radionuclides is dangerous.
Key point: For radium, combine nuclear decay with its calcium-like ion chemistry and internal distribution.
Where is radium found?
Short answer: In nature it occurs only in trace amounts as part of uranium and thorium decay series, including in some rocks and groundwater.
Natural radium forms in radioactive decay series associated with uranium and thorium. Radium occurs only in trace quantities as part of uranium/thorium decay series, not as large native-metal deposits.
Key point: Natural occurrence, resources, production and recycling are different geography questions.
What is radium used for today?
Short answer: Modern uses are limited. Radium-223 dichloride has a regulated medical role in certain prostate-cancer bone-metastasis settings.
Radium-223 medicine: Ra-223 dichloride is used in specific cases of prostate cancer metastatic to bone, under specialist clinical care. Scientific history: Radium was central to early radioactivity research and helped transform understanding of atoms and nuclei. Radium is chemically related to other alkaline-earth metals, but its radioactivity dominates its practical handling and modern uses. Historical luminous-paint use is now a safety lesson, not a recommended application.
Key point: Always distinguish the pure element from the compound, alloy, isotope or device material that actually performs the application.
Why was radium used in old watch dials?
Short answer: Radium compounds were historically mixed with phosphors to make self-luminous paint. The serious radiation hazards were not initially understood, and this use was abandoned.
Luminous-paint history Radium was once used in luminous paints; severe occupational harms helped establish major lessons in radiation protection. Radium is chemically related to other alkaline-earth metals, but its radioactivity dominates its practical handling and modern uses. Historical luminous-paint use is now a safety lesson, not a recommended application.
Key point: Use the direct answer together with the material, isotope and evidence context shown elsewhere on the page.
Who discovered radium?
Short answer: Marie Curie and Pierre Curie announced the discovery in 1898 while studying pitchblende residues.
In 1898, Marie Curie and Pierre Curie announced radium after studying highly radioactive pitchblende residues. In 1911, Marie Curie and André Debierne isolated radium metal through specialized laboratory work.
Key point: Discovery credit follows the historical evidence and accepted attribution, not just the earliest claim.
Scientific sources for Radium
- Royal Society of Chemistry - Radium
- NIST - Atomic Data for Radium
- NCI - Radium-223 and advanced prostate cancer
- EPA - Radionuclide Basics: Radium
- U.S. EPA — Radium
Questions to ask next about Radium
A good element lesson should lead to the next useful question, not end after a list of facts.
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