Ra Radium

Quick answerRadium (Ra) is an alkaline earth metal with atomic number 88 and a mass number of 226 (the most stable isotope), in group 2, period 7. It was discovered by Marie Curie and Pierre Curie in 1898. It is used for historical luminous paint and cancer treatment research. Its electron configuration is [Rn] 7s2.

Radium is the glowing element Marie Curie isolated, once painted on watch dials before its dangers were understood.

Key facts

Symbol	Ra
Atomic number	88
Atomic mass	[226] — mass number of the most stable isotope
Category	alkaline earth metal
Group	2
Period	7
Block	s-block
Electron configuration	[Rn] 7s2
Discovered	Marie Curie and Pierre Curie, 1898
Uses	historical luminous paint, cancer treatment research, industrial radiography, calibration sources

Quick quiz

Three questions from the facts on this page. No sign-up, no score is saved.

1. What is the chemical symbol of Radium?

Be Ra Ca Mg

2. What is the atomic number of Radium?

90 88 89 87

3. Which category does Radium belong to?

alkali metal alkaline earth metal noble gas halogen

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Keep exploring

• Periodic table — all 118 elements
• Beryllium (Be) — another alkaline earth metal, atomic number 4
• Magnesium (Mg) — another alkaline earth metal, atomic number 12
• Calcium (Ca) — another alkaline earth metal, atomic number 20
• Strontium (Sr) — another alkaline earth metal, atomic number 38
• Barium (Ba) — another alkaline earth metal, atomic number 56
• Marie Curie — discovered Radium
• Pierre Curie — discovered Radium

Sources & last updated

• CIAAW — Standard Atomic Weights
• PubChem Periodic Table
• Wikipedia — Timeline of chemical element discoveries

Last updated: 2026-11-12. Figures are shown with their year; where sources disagree, the value is left out rather than estimated.