Explanation:

* Electronegativity: Francium has a lower electronegativity than cesium, meaning it has a stronger tendency to lose its valence electron. This makes it more reactive.

* Ionization Energy: Francium has a lower ionization energy than cesium, indicating that it requires less energy to remove an electron. This again contributes to its higher reactivity.

* Atomic Size: Francium is larger than cesium. Its valence electron is further from the nucleus, making it easier to remove and therefore more reactive.

Conclusion:

Due to its lower electronegativity, lower ionization energy, and larger atomic size, francium is the more reactive element compared to cesium. However, it's important to note that francium is extremely rare and radioactive, making it difficult to study its reactivity in detail.