Which Is the Most Fundamental Reason Why Cesium Is More

Multiple Choice

Which is the most fundamental reason why cesium is more reactive than rubidium?

A) The effective nuclear charge on the valence electrons of cesium is less than the effective nuclear charge on the valence electrons of rubidium.
B) The electronegativity of cesium is less than the electronegativity of rubidium.
C) The atomic radius of cesium is larger than the atomic radius of rubidium.
D) The ionization energy of cesium is larger than the ionization energy of rubidium.
E) The ionic radius of cesium is larger than the ionic radius of rubidium.