Why is potassium more reactive than francium?

Here goes, In short: it's not. I think you got it the wrong way around, the order of reactivity of the alkali metals is as follows (Least reactive to most reactive): Lithium (Li) Sodium (Na) Potassium (K) Rubidium (Rb) Caesium (Cs) Francium (Fr) T... read more

Cesium is more reactive with water than potassium, and francium more reactive than cesium. If you happen to drop one of those in water, it would burn up at high speed, causing a blinding light (for heavy elements) and can make the water boil. read more

Francium is the largest atom within the group and has the least attraction between its valence electron and the nucleus so it loses an electron more easily than the other alkali metals. This same strong reactivity because of one valence electron is true of potassium, as well. read more

becomes more shielded by other electrons (because it is closer to the nucleus) and, therefore, is less likely to be involved in chemical reactions. Consequently, the reactivity of francium is significantly less than anticipated. read more