Vikas TU
Last Activity: 8 Years ago
Reposting the answer as U have asked twice, plz check your previous qstn.
Reanswering:
Caesium being in large size and has outemost sheels and orbitals as bulkier are easy too emit the electrons when comes under the UV radiations or any phtoelectric effect. Li being very small however used less than Cs as the enrgy reuired is more as due to the electrons embedded into it within deep.