Fr
Francium
Francium is a chemical element with the symbol Fr and atomic number 87. It has a mass number of 223, sits in period 7 and group 1, and is classified as an alkali metal.
Properties
| Symbol | Fr |
|---|---|
| Atomic number | 87 |
| Mass number | 223 |
| Category | Alkali metal |
| Group | 1 |
| Period | 7 |
| Electron configuration | [Rn] 7s1 |
| Outer-shell electrons | 1 |
The figure of 223 is a mass number rather than a measured atomic weight, because this element has no stable isotope.
Calculate with francium
- Molar mass of any formula containing it
- Electron configuration, including ions
- Effective nuclear charge by Slater's rules
- Average atomic mass from isotope abundances
Group 1
Atomic weights are the IUPAC 2021 standard values, abridged to the conventional five significant figures. Group, period, category and electron configuration are derived from the atomic number rather than stored, so they cannot drift out of step with it.