Fr Francium

Quick answerFrancium (Fr) is an alkali metal with atomic number 87 and a mass number of 223 (the most stable isotope), in group 1, period 7. It was discovered by Marguerite Perey in 1939. It is used for atomic research and spectroscopy studies. Its electron configuration is [Rn] 7s1.

Francium is so rare and short-lived that only a few grams exist on Earth at any time, and it has no uses beyond research.

Key facts

Symbol	Fr
Atomic number	87
Atomic mass	[223] — mass number of the most stable isotope
Category	alkali metal
Group	1
Period	7
Block	s-block
Electron configuration	[Rn] 7s1
Discovered	Marguerite Perey, 1939
Uses	atomic research, spectroscopy studies, testing atomic theory

Quick quiz

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

1. What is the chemical symbol of Francium?

Na K Li Fr

2. What is the atomic number of Francium?

87 86 88 89

3. Which category does Francium belong to?

transition metal alkali metal halogen noble gas

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Keep exploring

• Periodic table — all 118 elements
• Lithium (Li) — another alkali metal, atomic number 3
• Sodium (Na) — another alkali metal, atomic number 11
• Potassium (K) — another alkali metal, atomic number 19
• Rubidium (Rb) — another alkali metal, atomic number 37
• Caesium (Cs) — another alkali metal, atomic number 55

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.