Periodic Classification and Periodic Properties - Result Question 14
####11. Which of the following represents the correct order of increasing first ionisation 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) $Ca<Ba<S<Se<Ar$
(2013 Main)
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Answer:
Correct Answer: 11. (b)
Solution:
- Ionisation energy increases along a period from left to right and decreases down a group. The position of given elements in the periodic table is as
| Group No. 2 | $\mathbf{1 6}$ | $\mathbf{1 8}$ |
|---|---|---|
| $Ca$ | $S$ | $Ar$ |
| $Ba$ | $Se$ |
Thus, the order of increasing $\Delta H _{IE _1}$ is $Ba<Ca<Se<S<Ar$
