Question

Why are potassium and cesium, rather than lithium used inphotoelectric cells?

Answer 1

Allthe three, lithium, potassium, and cesium,are alkali metals. Still, K and Cs are used in the photoelectric celland not Li.

Thisis because as compared to Cs and K, Li issmaller in size and therefore, requires high energy to lose anelectron. While on the other hand, K and Cs have low ionizationenergy. Hence, they can easily lose electrons. This property of K andCs is utilized in photoelectric cells.