Question

The element having greatest difference between its first and second ionization energies, is:

• A. $Ca$
• B. $Sc$
• C. $K$
• D. $Ba$

Answer 1

The correct option is C $K$

$K$ has one electron, while $Ca$ & $B$a has 2 electrons and Sc has 3 electrons in their valence shell.
$K$, therefore after removal of outermost
$e^{-}$ acquire inert gas configuration and will therefore require large energy for the removal of next electron.
In other elements the difference will be less than that of $K$.
C is the correct option.