Radium is a radioactive element present in uranium ores. It was historically used in luminous paints, linking an early everyday application of radioactivity to a major lesson in material hazards. Its decay also produces radon, allowing one element's story to lead directly to another.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
Why did historical radium paint need a phosphor?
Radium salts combined with phosphors
FOLLOW THIS RELATIONSHIP
Separate the ingredients
Historical luminous mixtures combined a radioactive radium component with a phosphor. The two ingredients had different functions even though their contributions appeared together as visible light.
Explore the model (optional)
RaFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Optional: check your understanding
USE THE EXPLANATION
Which description correctly separates the two material roles?
Atomic identity, reference properties and structure models
INTERACTIVE 3D88 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Rn] 7s2. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
The Curies announced radium in 1898 after following unexpectedly strong in pitchblende residues. Separating its salts from chemically similar barium took prolonged work. Marie Curie and André Debierne isolated the metal in 1910, a different achievement from the original discovery. Radium’s subsequent use in luminous products and laboratories made radioactivity publicly visible, while the experiences of exposed workers transformed understanding of its risks.
1898
New element announced
The Curies identify radium through radioactivity and chemical separation.
1910
Metal isolated
Marie Curie and André Debierne obtain radium in metallic form.
Radium occurs naturally as a trace member of uranium and thorium series. It can accompany chemically similar alkaline-earth elements in and water. Its presence is therefore linked to both radioactive parents and local chemistry; a radium-containing mineral is not simply a deposit of pure radioactive metal.
Radium is an alkaline-earth element whose compounds commonly contain a +2 , giving it useful chemical similarities to barium. Radioactivity comes from its and continues when it forms compounds. Visible light associated with historical radium paint arose from radiation exciting a phosphor, not from a special glowing metallic surface.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
973 K
at standard pressure unless noted
Boiling point in K
2010 K
101.325 kPa
Density in g/cm³
5.5 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
0.9 Pauling
Pauling scale
First ionization energy in kJ/mol
509.3 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
221 pm
single-bond covalent radius
Common oxidation states
+2
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust
Not recorded
upper continental crust, mass fraction
Has stable isotopes
Noderived
Discovery year in CE
1898 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 7
Ra 0.9 Pauling · Radium
Electronegativity across period 7. Exact values.
Ra
0.9
Ac
1.1
Th
1.3
Pa
1.5
U
1.38
Np
1.36
Pu
1.28
Am
1.13
Cm
1.28
Bk
1.3
Cf
1.3
Es
1.3
Fm
1.3
Md
1.3
No
1.3
Lr
1.3
Electronegativity down group 2
Ra 0.9 Pauling · Radium
Electronegativity down group 2. Exact values.
Be
1.57
Mg
1.31
Ca
1
Sr
0.95
Ba
0.89
Ra
0.9
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
