Selenium (Se) is similar to sulphur in its properties and francium (Fr) is an alkali metal, What is the formula for francium selenite?

Francium is an alkali metal which is from the group 1. The element of the group 1 are Li, Na, K, Rb, Cesium and francium. The common oxidation state of all the alkali metal are +1. As we know, the selenium is showing the properties of sulphur because it also has the +1 oxidation. Hence, the formula of selenite is Seo3-2.
As we apply the crisscross rule we get, the formula for francium selenite is ${\mathrm{Fr}}_2{\mathrm{SeO}}_3$