Ra
Radium
Element 88 · Alkaline earth metal
Radium (Ra)
Radium is an intensely radioactive alkaline earth metal that glows faintly blue. Its discovery reshaped physics and medicine.
- Alkaline earth metal
- Period 7
- Group 2
- s-block
- solid at room temperature
- ☢ Radioactive
Key properties
- Atomic mass
- [226]
- u
- Electron configuration
- [Rn] 7s2
- Melting point
- 699.9 °C
- 973 K
- Boiling point
- 1,139.9 °C
- 1,413 K
- Density
- 5 g/cm³
- Electronegativity
- 0.9
- Pauling
- Atomic radius
- 283 pm
- van der Waals
- 1st ionisation energy
- 5.279 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about radium
- 01
The Curies processed tonnes of pitchblende to obtain a tenth of a gram of radium chloride.
- 02
The “Radium Girls” who painted glowing watch dials suffered severe radiation poisoning.
- 03
Radium-223 is still given as a treatment for prostate cancer that has reached the bones.
Applications
What is radium used for?
- Cancer treatment (Ra-223)
- Luminous paint (historically)
- Neutron sources
History
Discovery & name origin
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 88
- Atomic mass
- [226] u
- Group
- 2
- Period
- 7
- Block
- s-block
- Electron configuration
- [Rn] 7s2
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2
- Electrons per shell
- 2, 8, 18, 32, 18, 8, 2
- Electronegativity (Pauling)
- 0.9
- Electron affinity
- —
- Atomic radius (van der Waals)
- 283 pm
- Stable isotopes
- None — all isotopes are radioactive
Oxidation states
Highlighted: common oxidation states (+2).
Successive ionisation energies
Energy to remove each electron in turn (kJ/mol). Big jumps show where a new, inner shell begins.
- 1st509.3
- 2nd979
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 973 K · 699.9 °C · 1,291.7 °F
- Boiling point
- 1,413 K · 1,139.9 °C · 2,083.7 °F
- Density
- 5 g/cm³
- Molar heat capacity
- —
- Appearance
- Silvery white metallic
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Radium questions
What is Ra on the periodic table?
Ra is the symbol for radium, element 88 on the periodic table. It sits in group 2, period 7, in the alkaline earth metal category, and has an atomic mass of [226].
What is the atomic number of radium?
Radium has atomic number 88, so every radium atom has 88 protons in its nucleus. Its symbol is Ra and its atomic mass is [226].
Who discovered radium?
Radium was discovered by Marie Curie and Pierre Curie in 1898 (France). The name comes from Latin radius, “ray”.
What is radium used for?
Radium is used for: cancer treatment (Ra-223); luminous paint (historically); neutron sources.
Is radium a metal?
Yes. Radium is a alkaline earth metal, one of the metallic elements.
What is the electron configuration of radium?
The electron configuration of radium is [Rn] 7s2. Its 88 electrons are arranged in shells as 2, 8, 18, 32, 18, 8, 2.