Francium (symbol Fr, atomic number 87) is the second-rarest naturally occurring element, intensely radioactive. It is classified as a alkali metal and sits in group 1, period 7 of the periodic table.
Overview
Francium is the chemical element with atomic number 87 and the symbol Fr. With a standard atomic weight of [223], it is a alkali metal. In the periodic table it occupies group 1 and period 7, and under standard conditions it is normally a solid. Francium is the second-rarest naturally occurring element, intensely radioactive.
Atomic structure
An atom of Francium has 87 protons in its nucleus and, when neutral, 87 electrons arranged in the configuration [Rn] 7s1. Francium has no stable isotope; the value [223] refers to the mass number of its most stable or most commonly produced isotope.
Discovery and place in the table
Francium was discovered in 1939 by Marguerite Perey. It follows Radon (Rn) and precedes Radium (Ra) in order of atomic number.
| Atomic number | 87 |
|---|---|
| Symbol | Fr |
| Atomic mass | [223] |
| Category | Alkali metal |
| Group | 1 |
| Period | 7 |
| Electron configuration | [Rn] 7s1 |
| Phase at STP | Solid |
| Discovered | 1939 (Marguerite Perey) |