The set representing the correct order of the first ionisation potential is

Options

A. `K gt Na gt Li`
B. `Be gt Mg gt Ca`
C. `B gt C gt N`
D. `Ge gt Si gt C`

Answer

2

Explanation

Down the group the effective nuclear charge remains almost constant . But down the group with increasing atomic number the of atomic orbits increases and there by atomic size increases. As a result, the distance of valence shell electron from nucleus increases and attraction between them decreases and therefore ionization energy decreases.