Periodic Classification And Periodic Properties Ques 5
5. Which of the following represents the correct order of increasing first ionisation enthalpy for $\mathrm{Ca}, \mathrm{Ba}, \mathrm{S}$, Se and $\mathrm{Ar}$ ?
(a) $\mathrm{Ca}<\mathrm{S}<\mathrm{Ba}<\mathrm{Se}<\mathrm{Ar}$
(b) S $<$ Se $<\mathrm{Ca}<\mathrm{Ba}<\mathrm{Ar}$
(c) $\mathrm{Ba}<\mathrm{Ca}<\mathrm{Se}<$ S $<\mathrm{Ar}$
(d) $\mathrm{Ca}<\mathrm{Ba}<\mathrm{S}<\mathrm{Se}<\mathrm{Ar}$
(2013 Main)
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Answer:
Correct Answer: 5.(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 | $\mathbf{1 6}$ | $\mathbf{1 8}$ |
|---|---|---|
| $\mathrm{Ca}$ | $\mathrm{S}$ | $\mathrm{Ar}$ |
| $\mathrm{Ba}$ | $\mathrm{Se}$ |
Thus, the order of increasing $\Delta H _{\mathrm{IE} _{1}}$ is $\mathrm{Ba}<\mathrm{Ca}<\mathrm{Se}<\mathrm{S}<\mathrm{Ar}$
BETA
