Arrange the second period elements in the increasing order of their first ionization enthalpies. Explain why Be has higher `IE_(1)` then B.

Explanation

The increasing order of the I.E of `2^(nd)` period elements are as follows:
`{:(,Li lt ,B lt ,Be lt ,C lt ,O lt ,N lt ,F lt ,Ne),("IE values",(520),(801),(899),(1086),(1314),(1402),(1681),(2081) "KJ/mole"):}`
.B. has a lesser IP than .Be..

`rarr` Due to presence of incompletely filled p-orbitals in Boron, its IE values is less.
`rarr` Due to presence of completely filled `s^(2)` configuration in .Be., it has higher IE values.