On the periodic table, francium is commonly identified as having the largest atomic radius in the standard periodic trend. It is an alkali metal in group 1, period 7, with symbol Fr and atomic number 87. Atomic radius generally increases down a group and decreases from left to right across a period.
Francium is extremely rare and radioactive. It occurs naturally in tiny amounts as a product of radioactive decay, especially in uranium and actinium decay chains. Marguerite Perey discovered it in 1939 while studying actinium, and she named it after France.
The exact numerical ranking of atomic radii can vary slightly with the measurement or definition used, especially for super-heavy and highly reactive elements. In school-level periodic trends, francium is the accepted answer because it lies at the bottom-left corner of the table. Cesium is the largest stable, naturally abundant alkali metal.