Francium

01 / A closer look

Meet Francium

Francium has atomic number 87: every atom of this element contains 87 protons. It belongs to period 7, group 1 of the periodic table.

In a neutral atom, the number of electrons equals the number of protons. Isotopes of this element share the same atomic number but have different neutron counts.

02 / Physical properties

Melting point

294 K

Reference estimate; not an established bulk measurement

Boiling point

923 K

Reference estimate; not an established bulk measurement

Density

Not listed

Isotope mass number

[223]

Melting points, boiling points and densities follow RSC fact boxes. Density is referenced to room temperature; consult the source for pressure and allotrope details. These are reference values, not a claim that every value was experimentally measured. Atomic weights follow CIAAW.

Physical-property source: Royal Society of Chemistry ↗ · Reviewed 24 September 2026

Standard atomic weights follow CIAAW 2024 (abridged). Brackets show an isotope mass number from IUPAC 2022, not a standard atomic weight.

03 / Atomic structure

Atomic structure

Electron configuration

[Rn]7s1

Oxidation states

+1

Electronegativity · Pauling

0.7

First ionisation energy

3.9 eV

Atomic radius

348 pm

04 / Where it is found

Where it is found

Minute amounts in natural decay chains; also synthesised.

Production and export figures depend on the commodity and reporting year. No comparable country quantities have been included for this element in this edition.