Francium

Alkali metal · atomic number 87

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Francium is a chemical element with symbol Fr and atomic number 87. It used to be known as eka-caesium and actinium K. It is the second-least electronegative element, behind only caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon.

Properties of Francium

Element category	Alkali metal
Atomic number	87
Atomic mass	223 u
Phase at STP	Solid
Group	1
Period	7
Block	s
Electron configuration	[Rn] 7s1
Electrons per shell	2, 8, 18, 32, 18, 8, 1
Electronegativity (Pauling)	0.79
Melting point	300 K (27 °C)
Boiling point	950 K (677 °C)
Density	1.87 g/cm3
Discovered by	Marguerite Perey

← Radon · Periodic table · Radium → Ra

About the alkali metal group

Soft, wildly reactive metals of group 1 — they fizz in water and never occur pure in nature. Lithium, sodium, potassium and friends.

Data: Periodic-Table-JSON (CC BY-SA 3.0) · stored statically on our server. https://en.wikipedia.org/wiki/Francium

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🧪 Reactive nonmetal

11 elements: Elements that readily gain or share electrons — the building blocks of water, air, living tissue and most organic chemistry.

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6 elements: Full outer electron shells make these gases almost inert: they barely react, glow in discharge lamps and are used to create unreactive atmospheres.

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6 elements: Soft, wildly reactive metals of group 1 — they fizz in water and never occur pure in nature. Lithium, sodium, potassium and friends.

🧪 Alkaline earth metal

6 elements: Reactive group-2 metals a step calmer than the alkalis: magnesium, calcium and the structural and biological workhorses among them.

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