Periodic table › Radium
1. Identity and classification
Silvery-white, lustrous, moderately soft metallic solid
- Name and symbol
- Radium (Radium) · Ra
- Atomic number
- 88
- Relative atomic weight / mass number
- [226]
- Group · period · block
- 2 · 7 · s
- Category
- Alkaline Earth Metal
- State near room temperature
- Solid
- Stable isotopes
- No stable isotopes
- CAS number
- 7440-14-4
Square brackets [A] indicate a representative isotope mass number, not an average atomic weight. Neutron counts differ between isotopes.
2. Atomic structure and electron configuration
- Protons · electrons in a neutral atom
- 88 · 88
- Neutrons in reference isotope
- 138 (226Ra)
- Full electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 7s²- Abbreviated configuration
[Rn]7s²- Electrons per shell
- 2, 8, 18, 32, 18, 8, 2
- Listed oxidation states
- +2
- Electronegativity
- 0.9 (Pauling)
- First ionization energy
- 509.346 kJ/mol · 5.279 eV
- Electron affinity
- Not established
- Covalent radius
- 221 pm
- van der Waals radius
- 283 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 5 g/cm³
- Melting point
- 973 K · 699.85 °C · 1291.73 °F
- Boiling point
- 1413 K · 1139.85 °C · 2083.73 °F
- Crystal structure
- BCC
- Specific heat
- 0.094 J/(g·K)
- Thermal conductivity
- 18.6 W/(m·K)
- Enthalpy of fusion
- 8.5 kJ/mol
- Enthalpy of vaporization
- 113 kJ/mol
- Magnetic ordering
- Paramagnetic
- Mohs hardness
- Not established
- Speed of sound
- Not established
Density and structure depend on temperature, pressure and allotrope. 25°C is a room-temperature reference, not STP. Unestablished values are not zero.
4. Chemical behavior and compounds
The +2 oxidation state is common; beryllium compounds show substantial covalent character.
Selected compounds: RaO / Ra₂O₃ (Oxide) · RaClₙ (Chloride) · RaFₙ (Fluoride)
Reaction reference
Oxide layers form in air; the behavior depends on temperature and the metal.
Reactivity with water increases broadly down Group 2; beryllium and magnesium differ from the heavier members.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 226Ra | Radioactive | — | 1600 Y |
Half-life units: s seconds, m minutes, h hours, d days, Y years. A dash means no natural-abundance value is given, not zero. Listed records are selected ground states; metastable states are distinct.
6. Discovery and occurrence
- Discovery
- 1898 CE
- Scientists associated with discovery
- Marie Curie, Pierre Curie & Gustave Bémont
- Location
- France (Paris)
- Origin
- Trace Natural / Synthetic
- Listed crustal abundance
- Not established
Minerals and naming reference
Trace in Uraninite / Pitchblende ores
Named from scientific/historical roots associated with Radium (Ra), discovered or characterized by Marie Curie, Pierre Curie & Gustave Bémont.
7. Applications
Radium-223 dichloride (Xofigo) targeted alpha therapy for bone metastases; historical radioluminescent dials and Curie radioactivity standards
Detailed applications by field
- everyday
- Radium-223 dichloride (Xofigo) targeted alpha therapy for bone metastases; historical radioluminescent dials and Curie radioactivity standards
- industry
- Used in alkaline earth metal processing, specialized alloys, and chemical manufacturing (Radium-223 dichloride (Xofigo) targeted alpha therapy for bone metastases; historical radioluminescent dials and Curie radioactivity standards).
- electronics
- Applied in electronic components, semiconductors, or functional coatings where Radium's electronic structure ([Rn] 7s²) provides target conductivity.
- medicine
- Diagnostic imaging, biomedical instrumentation, or pharmaceutical synthesis research.
- energy
- Utilized in power generation, battery materials, catalysts, or nuclear technology involving Radium.
- aerospace
- High-performance materials, structural alloys, or space instrumentation utilizing Radium.
- agriculture
- Not used in agriculture due to radioactivity or heavy-metal toxicity.
- science
- Spectroscopic standard, crystallography, and quantum chemistry studies of Period 7 s-block elements.
8. Biological role and safety
Hazard depends on the isotope, chemical form, dose and exposure route.
Elemental substances, ions, compounds and radioisotopes can have different health effects. This is an educational reference; laboratory work requires the material safety data sheet and trained supervision.
Biological role reference
Classified as highly radioactive / synthetic in human and biological systems.