What Is Francium?
Francium is a chemical element with the symbol Fr and atomic number 87, classified among the alkali metals in Group 1 of the periodic table.
The second rarest naturally occurring element and the most unstable. Named after France.
As a alkali metal in Period 7 and Group 1 (Alkali Metals), francium's placement on the table reflects its electron configuration of [Rn] 7s¹, which governs its bonding behavior and the type of compounds it typically forms.
Position on the Periodic Table
Francium is located in Period 7, the bottom row of the standard periodic table, consisting largely of radioactive and synthetic elements.
Within that row, francium sits in Group 1 (Alkali Metals), alongside elements that share a similar number of valence electrons and, by extension, similar chemical behavior.
This position is not arbitrary — the periodic table was deliberately organized so that an element's row and column reveal its expected reactivity, bonding pattern, and physical state at a glance.
Physical & Chemical Properties
Francium has an atomic mass of (223) u and a density of ~2.48 g/cm³. Its melting point is 27°C and its boiling point is 677°C.
Francium is soft enough to be cut with a knife and never appears as a free element in nature, since it reacts too readily with moisture and oxygen in the air.
Electron Configuration Explained
Francium's electron configuration is [Rn] 7s¹, describing how its electrons are distributed across shells and subshells around the nucleus.
Reading the configuration in order shows electrons filling shells of increasing energy, following the standard Aufbau principle that explains how atomic structure builds up across the periodic table.
The outermost (valence) electrons shown in this configuration are what ultimately determine francium's chemical reactivity and the type of bonds it forms with other elements.
History & Discovery
Francium was formally discovered in 1939, M. Perey, identified through the careful isolation and analytical techniques typical of that era's chemical research.
Many elements from this period were anticipated by Dmitri Mendeleev's periodic table, which successfully predicted gaps corresponding to undiscovered elements well before laboratory instruments existed to confirm them directly.
What Is Francium Used For?
Francium's specific properties make it useful in several applications, including:
- Research only
- Scientific study
- Atomic structure research
- No commercial uses
- Historical medical research
These uses reflect francium's underlying classification as a alkali metal, since the same properties that define its category in chemistry also determine where it becomes practically useful.
Fun Facts About Francium
- Fewer than 30 grams of francium exist in Earth's entire crust at any one time.
- Francium is element number 87 on the periodic table, in Period 7 and Group 1.
- Its standard atomic mass is (223) u, calculated from the natural abundance of its isotopes.
Frequently Asked Questions
What is Francium's atomic number?
Francium has atomic number 87.
What is Francium's chemical symbol?
Francium's symbol is Fr.
What group and period is Francium in?
Francium is in Period 7, Group 1 (Alkali Metals).
What is Francium's atomic mass?
Francium's standard atomic mass is (223) u.