Which of the following atoms has the lowest ionization potential ?

Options

A. `""_18^40Ar`
B. `""_55^133Cs`
C. `""_8^16O`
D. `""_7^14N`

Answer

B

Explanation

Out of the given four atoms, `""_55^133Cs` has the largest size. Hence the electrons present in the outermost orbit will be at larger distance from the nucleus.
`therefore` r is maximum and the coulomb's force
`F= (1)/(4piepsi_0) (Qxxe)/(r^2)` produced by the nucleus on the electrons will be minimum.
`therefore` The energy required to liberate the electron from the outermost orbit will be minimum.
`therefore` Ionisation potential will be minimum for `""_55^133Cs` .