Question

Which of the following represents the correct order of increasing first ionization enthalpy for $Ca$, $Ba$, $S$, $Se$ and $Ar$?

• A. $Ca<S<Ba<Se<Ar$
• B. $S<Se<Ca<Ba<Ar$
• C. $Ba<Ca<Se<S<Ar$
• D. $Ca<Ba<S<Se<Ar$

Answer 1

The correct option is C

$Ba<Ca<Se<S<Ar$

Let's just write electronic configuration of all the elements in question.

$Ca\to 1S^{2}2S^{2}2P^{6}3S^{2}3P^{6}4S^2$

$Ba\to \left[Xe\right]6S^2$

$S\to 1S^{2}2S^{2}2P^{6}3S^{2}3P^4$

$Se\to \left[Ar\right]4S^{2}4P^4$

$Ar\to 1S^{2}2S^{2}2P^{6}3S^{2}3P^6$

As we know,

$Ionizationenergy\propto \frac{1}{AtomicRadius}$

As we know,

$Ba>Ca>Se>S$[Atomic Radius]

Therefore,

$S>Se>Ca>Ba\left[I{E}_1\right]$

And if we have to remove one electron from a noble gas, then we have to apply large amount of energy because noble gases are very stable.

Therefore, the correct order will be

$Ba<Ca<Se<S<Ar.$

Too easy. Right!!!